yes everyone thinks that if you have a 3.0ghz processor but only 256MB of ram your computer will be fast but in reality it would be better if you had a 2gz processor and 1GB of ram
if you want a PC that won't freeze up on you then 1Gb should be plenty. anything less than 1Gb isn't very good for multitasking and so on. Also, if you want to speed up your PC get a program like CCleaner and clean all the junk out once in awhile. Also try cleaning out the startup items via MSCONFIG and that will help speed up things a bit.