Keep in mind also however, that some of Microsoft's OS recommendations have tended to be a bit on the conservative side. Such as when the recomendations for win 95 were
* 486 DX
* 8 MB RAM
* ...
Ugh, even with a Pentium 75 and 8 MB of RAM, win95 ran like crap, and was one of the absolute worst experiences I've had wrt a computer in my life
It wasn't even running programs on top, as Explorer.exe would routinely crash, till I had more RAM in the system, with no programs running at all. It would be like "A program has performed an illegal operation:" Get details, and
Explorer.exe has caused an invalid page fault in krnl32.dll, at...
Most people outside of Redmond were saying you want at least 16 MB for win95... In fact, bye, and bye, doubling their RAM recomendations on the OS might not be a bad idea:
with
• A modern processor
• 512MB of system memory or more, and
• A graphics processor that will support Windows Display Driver Model (WDDM)
I say this in part, because from experience, 512 MB RAM on winXP Pro alone, (forget Vista) had started resulting in too much swapping and had become somewhat painful (though no where's near the 8 MB on win95). It was fine a couple years ago, but now 1 GB really is better. Don't expect Vista to run any better, then what many of us are seeing on winXP Pro today (with the same amount of RAM)...
Now does that mean everyone needs 1 GB on winXP Pro today? No, and for most years I had it, 512 MB, and before then 384 MB wasn't bad... But many of us have found that 512 MB just doesn't cut it anymore, as it used too...
Still, that's looking more at a computer that can run Vista reasonably well, which the comps many of us have currently will likely do. That isnt' talking something that will exploit, and make use of new features it has been designed to support; some of which like DX 10 (and the equivallent hardware to make use of all it's new features), hasn't been marketed yet...