NOTE: this thread is updated periodically
The most overlooked aspect of a new computer is its compatibility with older hardware and software.
Someone wants to upgrade their computer. Let's say they have a Pentium 3 600. That's a slot 1 setup with PC100 memory. This person's first instinct is going to be to upgrade the CPU. This is a bad idea because any slot 1 CPUs that are still around are too expensive and too hard to find. If this were a Tualitin P3 board (uses FCPGA2 processors) then it might be worth an upgrade depending on what CPU is in there and what CPUs are available. The same applies for AMD slot A CPUs -- they are in the same boat with the slot 1 P3. However, if you have an AMD Athlon Thunderbird or Duron CPU, that can easily be ported to any modern AMD motherboard so if you're on a tight budget and can only afford a motherboard and RAM right now, you can keep the old CPU for a while. If this person has 128MB of RAM, it would pay to get another 256 or so. 512 or more is usually overkill (costs too much, won't see much of a performance increase) for a system this old. In most cases it will be better to get a new motherboard, CPU, and RAM and keep the old hard drive, floppy drive, CDROM, and any peripherals. So let's say this person is in the market for a serious upgrade to a Pentium4 or AMD Athlon XP...
Speaking of drives and peripherals, are they going to work with your new parts? If the CDROM is at least a 4X (meaning it's probably IDE) then it is likely to work with your new system -- but a new CDROM is extremely inexpensive ($30 or less for a 52X) and it would make sense to buy a new one. DVD-ROM drives will also read CDs and are not very much more than that (around $50). Even a CDRW would cost about the same price. A floppy drive is a floppy drive... unless it's more than five years old, it's worth keeping it. The hard drive is almost certainly IDE, so that's safe to put into the new system.
What about your video card? If it is PCI, it will work with any new computer -- but you'll get much better video performance out of an AGP card. If your old system had an AGP video card, you must make sure that it is 1.5v or else it will not work in a new computer. If you're not sure, then get a new low-end video card (around $75 and it'll be much better than your old one). Don't bother porting your old sound card to your new computer; all new motherboards come with onboard sound and it's probably better than your old sound card anyway. The exception is if you have something like a Live Platinum with the frontpanel LiveDrive, or an Audigy2 or something special like that. Is your modem ISA or PCI? If it's ISA, get a new PCI modem card.
If you have an old scanner, is it SCSI? If you don't know, look in the manual or on the manufacturer's website. If it is SCSI, then make sure your SCSI card is PCI. If it's ISA (plugs into a black connector on the motherboard) then it can't be ported to a new computer. A new PCI SCSI card will run about $70, which is just a few dollars shy of a brand new USB scanner that will do twice the resolution of that old scanner you've got now. I can't tell you how many times I talk to people who have run into this problem.
Make sure your new motherboard has a parallel port for your old printer. While they do make parallel to USB adapters, they are usually about $20 and that's money you don't have to spend if you get the right motherboard.
Will Windows 98 work on your new computer? Maybe, maybe not. If it's Win98 SE (second edition) then it will probably work, but you might have a lot of trouble finding the right drivers. Will Windows NT work? Maybe, but probably not the way you want it to. Windows 95? Forget it! Windows ME will work, if you can deal with the system crashing twice a day. Windows 2000 should work perfectly. Windows XP Home or Pro will work best -- you'll get best performance and compatibility with Windows XP. Do you need Home or Pro? Well if you're not on a business network and not planning to set one up in your home, then XP Pro is a waste of money. Home edition will allow you to set up a ten node workgroup-based home network, which is what you'll be setting up if you do decide to network your home computers. Linux is a fun operating system for the technically minded and for those who like to tinker; if you're looking for a desktop OS to replace Windows, you'll need to go with a desktop distro like SuSE, Mandrake, Xandros, Lycoris, or Lindows. I suggest dual-booting with both Linux and Windows to start out with. While Linux is usually free, Windows is not -- don't borrow Uncle Harvey's Windows CD. Buy your own. It's legal, it's more convenient for you, you get free installation support, and it will work correctly whereas a pirated or borrowed copy will not have any of these things. Usually you will need to reinstall your operating system if you change the motherboard/CPU/RAM due to driver, registry and resource conflicts.
All new computers use PS/2 mice and keyboards (except for a few Abit boards that only use USB keyboards and mice). If you have a serial mouse it will still work, but an AT-style keyboard will not (they do make adapters from AT to PS/2, but it's probably better to get a new keyboard).
Will your old monitor work? If it's less than five years old, yes. There are a few models of LCD monitors that use a DVI connector instead of the standard 15-pin VGA connector that monitors have been using for many years. The DVI connector is white and rectangular; when you buy a new monitor make sure it will work with your video card. Most new video cards are dual-head (meaning they support two displays at once) and support both DVI and 15-pin, but check to make sure anyway.
Will your old power supply work? It needs to conform to the ATX 1.2 standard, which means that first of all it has to be ATX... if the case doesn't have a small rectangular I/O faceplate on the back where the keyboard, mouse, serial/parallel ports plug in (among others), but instead has one big round keyboard connector and a bunch of knockouts for serial and parallel ports, then discard the case and get a new one; do not get out your sawzall and start cutting it up to make the new motherboard fit. If the power supply uses two white connectors (side by side) to get power to the mainboard instead of one larger connector, then it is an AT power supply and won't work with a new board. If you have an older ATX power supply (more than two years old) then it's a fairly safe bet that you'll need a new one. You need at least 200w of output for a basic system (300w or more if you have a lot of high-powered peripherals or more than two IDE drives) and there should be a small square power connector that has two yellow wires and two black wires. This is an additional power connector that must be used for all Pentium4 boards and some newer AMD boards, but even if you've got an AMD board that doesn't require it you'll still need a newer-style ATX power supply for it to work properly. There's more to it than this, so if you're that interested then here's a link to the exact specifications: http://www.formfactors.org/developer/sp ... PSDGV1.pdf
What are you forgetting? Make a checklist of the things you need to build a full computer, including the motherboard, CPU, RAM, video card, sound card, hard drive, CD drive (DVD drives and CDRWs count), floppy drive, operating system, ATX case with power supply, monitor, mouse, and keyboard.
If you're buying an Intel Pentium 4 retail box CPU, you will not need an aftermarket heatsink and fan for it -- it comes with one that is very good and will last forever. The newer AMD retail CPUs have good heatsink/fan units, but the older ones were horrible. Check to make sure that your HSF has more than one retention clip on each side -- the ones with the single prongs have been known (in rare but not unheard of instances) to pop off and cause the CPU to overheat and fail. While this isn't a frequent problem, it does happen and an aftermarket cooling solution will serve you better in the long run. In most cases you don't need more than one 80mm case fan in your computer case unless you've got more than two IDE drives (hard drive and CDROM) or unless the ambient temperature in the room will be above 70 degrees F.
OEM or Retail Box? It's up to you. OEM parts carry less of a warranty and the manufacturer will not give you any tech support. OEM CPUs will require an aftermarket heatsink/fan as they do not come packaged with one.
If you're using Linux, you'll want to get a distro with a modern kernel (2.4.19 or better). If you don't you might not be able to immediately install all of your peripherals. This is especially important if you're using the onboard LAN (specifically the Realtek chip) to connect to the Internet; if you're using an older kernel, chances are it won't recognize your onboard NIC and you won't be able to connect to the Internet for updates. If you must use an older kernel, keep a spare 3Com or other long-supported brand name network card around for installation purposes. Linux also has occasional trouble with motherboards that use SiS chipsets, so if you're planning on buying a SiS-based board you may want to pay a visit to http://www.linuxhardware.org
Some common questions I hear every day:
"Should I go with AMD or Intel?" There are a few things to consider: Intel CPUs are easier to install, usually operate at lower temperatures, and are in general of a higher quality of manufacture which means less failures. Intel is not always more expensive than AMD -- the prices fluxuate about once every four to six weeks, so make no assumptions on value before you've checked prices. Usually though, AMD is cheaper and their CPUs are just as fast as Intel's. CPU speed is only one factor in system performance though; your motherboard, RAM, and video card can have just as much of a role in overall system performance as your CPU does.
"Should I get a motherboard with onboard peripherals?" Sure, why not? LAN and sound are fairly standard onboard peripherals and work just as well as their PCI counterparts. Onboard video can be disabled and an AGP video card installed if you want to upgrade it in the future. It will be cheaper to get a motherboard with onboard peripherals than it will be to get the same peripherals separately. Often times a motherboard will have several different editions that are differently packaged; the Asus P4PE for instance has five different options packages. If you don't need things like 1394 or SATA support, don't waste money on the more expensive editions.
"Should I wait for the next great computer innovation?" If you don't need a new computer now, then sure -- wait for whatever you think you need. If a new computer can benefit you right now, then don't wait.
Some basic recommendations:
If you're a gamer, you need good 3D video performance, a fast hard drive, and high memory bandwidth.
If you're a home user who is just getting into computing, a motherboard with onboard video, sound, and LAN will be perfect. You can find both Intel and AMD-based motherboards that will fit your needs.
If you're looking for a business machine that needs a lot of computing power coupled with a lot of high-end options like AGP Pro and PCI-X, you'll probably want a dual-Xeon system. Some manufacturers that specialize in high-end motherboards are Intel, Supermicro, Iwill and Tyan, although Asus also makes a decent Xeon motherboard. You really don't want one of these machines for gaming. Think of a dual-CPU system as a team of workhorses, and a gaming machine as a racehorse. The workhorses will pull more of a load and get more work done, but the racehorse will be more fun to ride.
If you need a lesser-powered business machine, there are a wide variety of options available to you for motherboards and system components. When reading reviews and commentaries it's easy to get carried away with wanting high-end equipment. Keep in mind that the newest $500 3D video card will give you just as good a picture as a $50 ATI or Matrox card when you're not doing 3D rendering (CAD, 3D modeling, 3D gaming). Fastest and newest does not mean "Best" and certainly does not always mean "right for your needs."
For video editing, you need a fast CPU and at least 512MB of RAM. For 2D graphics and video editing, memory bandwidth isn't quite as important as it is to someone who is doing 3D rendering so just about any modern DDR or Rambus motherboard will work fine. For a top-end video editing setup I would recommend two hard drives -- one for the OS and programs and one empty drive to stream your video to/from. You don't need RAID for this, and you don't need a high-powered 3D graphics card. Your best bet is a Matrox or low-end ATI video card and the fastest processor you can afford. Intel's Hyper-Threading Technology will give you a noticable advantage here.
Don't ignore a brand just because you've never heard of it before. Many people will recommend Asus and Intel because they're popular, but you'll also find high-quality boards from lesser-known manufacturers like Iwill, Supermicro and many others. If you're thinking of getting a new motherboard, post a message asking for opinions on it and see what people say and remember to take into account the fact that a certain percentage of motherboards are guaranteed to fail. Also keep in mind that message forums are sometimes the only outlet that upset customers have to strike out at manufacturers; trust no rumors, rely on no single review, and get as many opinions as you can from people who have actual experience with the hardware in question.
If you have specific questions about upgrading or would like to ask for some recommendations on motherboards, it might be more helpful to you to post a new thread in the Recommendations forum where more people will see it rather than tack onto this thread, which many of the regular posters and moderators do not usually check.