Vista is still rather new, with a lot of kinks to work out. You can search this Forum and find some "user comments" on Vista. I've played around with Vista, and it appears to work. However, XP is much more stable and "comfortable".

If you opt for a 64-bit OS, CAESAR II will run in "32-bt emulation mode". We don't have a 64-bit edition of CAESAR II.

Installing CAESAR II on a server, either 2003 or 2008 shouldn't present any problems, since it actually runs on your workstation. Having said that, be aware that we haven't tested "2008 Server" at this time.