Ouch, 512k l2 cache.

I would honestly look to build a completely new computer. You need to get off that ancient DDR platform

Get a proc with at least 1mb cache, preferably 2mb. Dual core too.

Otherwise make sure all your graphics settings are waaaaaay down, also try running in a lower resolution. That should relieve some of the choppiness. Otherwise on that computer it will pretty much always be choppy.

First and easiest upgrade is to get another 1-2gb of RAM.