You can us XP or Win2000 (Maybe even ME ... not 100% sure about that). If you're running into memory problems with CS, try reducing the amount of memory allocated to the program. I know that seems counter-intuitive, but you've got to save some memory for the OS and any other programs that are running. Drop your PS allocation to 55% and see what happens. Also, you may want to use Task Manager and MSCONFIG to get rid of unneeded programs and services that are running in the background. This page may be of some help: http://www.adobe.com/support/techdocs/318243.html
One of the best things you can do to speed up PS is to use a second, large, fast hard drive for PS's scratch disk. Shel > [Original Message] > From: David Mann > If you plan to install Photoshop CS you'll need Windows XP. Or a > certain other platform which I shall not mention ;) I don't really > find processor speed to be a big issue but memory is something you > can never have enough of. Unfortunately 1Gb sticks are expensive. > > The memory management of CS is a bit annoying because it never > releases memory. I start running into problems (slowdowns) when it > hits about 1.2Gb. If I'm only doing one scan then I'm generally OK > but with multiple big scans I sometimes need to restart PS. I think > the scanner driver needs a fair bit of memory (I run it from within PS).

