When you buy a Dell or whatever, as much as you pay for it, run the most up to date OS with all the bells and whistles. Get as many features as affordable too. That said, a Mac runs OS X only for me. Vista Ultimate for a new OEM. For a build, I use Ubuntu Studio 8.04 and it's upgraded every 6 months to the newest release, but having XP that transfers over to the new computer as well. One license, one system.
Linux, stable and reliable OS with a 3d desktop, every application for free, Open Office 3 will support Office 2007 file formats come September when it's released. I see no reason to buy a Microsoft product for awhile in my home. Don't worry though, I spend what I save on gasoline and food. :wink: