Building the GEARBOX: Take on Borderlands 2 With the Ultimate $2500 Gaming PC
The OS: Windows 7 Professional
If you're building a gaming rig today, you may be tempted to install the Windows 8 Release Preview and hedge your bets until Windows 8 is released in late October. There are certainly pros and cons to that approach. For a productivity machine that would probably be fine, but serious gamers will probably want to stick with Windows 7 until Windows 8 is generally available and graphics drivers have matured.
Normally I'd recommend Windows 7 Home Premium for a gaming build like this, but Windows 7 Professional just seemed to be a better fit for this type of machine, particularly since it is frequently on sale. The professional SKU gets you a few added perks, like Remote Desktop Host support and Bitlocker drive encryption.
On a bright note, you'll be able to upgrade to Windows 8 for $40 this fall if you want Redmond's latest and greatest.