I have a 5 year old PC with 4 GB of RAM, i7 Intel processor running Windows 7 64 bit configuration and everything works fine. I don't have any special graphics card, just the one that came on the mother board. My Dell laptop works with less computer power with an i5 Intel Processor running Windows 7 64 bit configuration and 4 gigs of RAM. All works well I don't have any experience trying SketchUp on a Mac but my friends who have Macs use it without fuss. Unlike AutoCad, I don't believe you need a super fast graphics card. Of course the more RAM you have in either the graphics card or operating system, the faster it would run. I don't know of anyone still using Windows Xp as that is no longer supported by MS. Also Vista has not been a big favorite for the more graphical programs. I'd advise you to upgrade to Windows 7 if you're running Vista.