*Crisis*.. choppy graphics, takes forever to load things

I'm running an NVIDEA GeForce 6200A-LE graphics card and 512 MB RAM, (Micron
pc clientpro w/ pentium II 1.80 ghz) and it used to work great, but now i
have really bad performance while playing video games, and even XP-related
things and internet webpages that ran no problem are running extremely
choppy/slow and slowing down just about everything. I have no idea what the
problem is... I've tried everything i can think of to make the display run
faster (defrag, other performance/maintenance stuff) tried changing the
graphics card's settings, still no dice. There weren't any problems with it
until i didn't use my computer for about a month, and then it started running
even slower than usual. Not sure what to do next, can anyone help?