As far as I understand, Revit Architecture 2008 is compatible with 32 and 64 bit versions of Windows Vista. I also know that it works with 32 bit Windows Xp, and since it works for that and 64 bit vista, I would imagine that it will work with 64 bit xp as well. The RAM is really up to you. I have run it with 2 gigs just fine, but if you are doing renderings with Revit, more would be better. Dual Core is pretty much mainstream now, but you don't have to have dual core to run Revit 2008. I have a Prescott Intel 3.4 Ghz hyperthreading on my laptop and it works great with that. A good video card would be something to consider as well though. I think as of now, Intel Dual/Quad Cores have pretty much blown AMD out of the water, although i hear rumors that AMD will pop back soon with some competition. Hope this helps.