Let Microsoft itself tell you:
http://www.microsoft.com/windowsvist...y/capable.mspx
I'm no expert but here you go my two cents. You're especially low on RAM and believe me, you don't want to be. Windows in general is a natural RAM eater --more so Windows Vista-- and take into account that you'll need more to run other programs, nowadays all waste loads of RAM --this is tenfold true for open source programs. As for myself I'm fine with my XP even though my computer is new and "Premium Ready PC" and I'm not going to change my OS, but even if you want so badly to run Vista for some reason, I wouldn't recommed doing so with less than 1 Gb of RAM; I woun't recommend anyone using Vista if his machine isn't "Premium Ready", even if it's "Vista Capable", he would only get a slow and cloggy machine. Anyway the RAM is most easily expanded compared to other features. Also I heard Vista has 3D features so the graphic card does matter.