get radegast and run a text only client, only other solution is to rip out everything inside and start fresh, it would need a somewhat capable GPU to run SL, the 2400 series is what Secondlife considers Class Zero Hardware, mine is about Class 4 or 5 and gets about 30 fps depending on the amount of avatars in view, tho im running a viewer that i compiled myself.
to sum up everything, to run secondlife you have to have a decent cpu with good bandwith between ram and cpu, and a solid gpu, id recommend an athlon ii x2 or x4 at the least, 4 gig of ram, and a radeon 5770 or gts450 to get some okay framerates there. secondlife is still a pretty demanding program, however with the viewer 2 builds coming through the snowstorm development process, things are getting a bit better in terms of performance.