I wouldn't count on it......you might be able to run xp but not vista.....either upgrade your pc completely or buy a new one.....

My system is as follow :

AMD Athlon XP 2600+ 2.1GHZ
512mb of RAM
Nvidia Geforce 6200 256mb of video memory

Already I can run Vista well with my current pc setup, although I can't run aero....I can still run vista with all the other settings set on !

I'm planning on upgrading my system soon.....