XP does run on much older hardware than you might expect at least would as my former work laptop could not update to SP1 (specs PIII 650, 6GB HD, 256 ram "yes that was max ram")its fan died and I did notknow till it was to late (cooked). However I do have a have another machine for programming PLCs other than my work laptop and it runs SP1 (specs PIII 400, 6GB HD, 1.3gig Ram). Know it well as I just got done moving keys from laptop to the other machine and a usb drive. LOL Froze the laptop overnight just for that purpose..
Any way on the Win 7 front I have just ordered a new drive for my win XP daily driver to install 7 on. As I don't cotton up to Windows all that much I have had to fall back to it since my husbands PC went south (Slackware) and I turned over my main machine to him (Slackware). It is better for him to have such a machine OS as the sites he likes to visit during his private time is a bit 'risque' for a Windows box..
My XPs are tweaked way out and trimmed with all the possible goodies one might expect from a geekette. As a matter of fact it has many of the same tools as my Slackware box in their win flavors...
AND remember to support the open source software. If you use it - DONATE!! It is that simple..
Now if they would just make windows as easy to configure as Linux we would be good to go..
Did I say that???