Try installing ubuntu linux, and use the linux viewer. That will provide a system boost. (ubuntu ... Or more specfically wubi, will install linux as a dual boot with a minor hastle involved Of course this solution might be way hard... But the only other solution would be to upgrade your computer, because 512Mb isn't really enough RAM to run even windows XP at it's best.
Also if your computer has on board graphics you will not be able to run SL at it's best.
Thus, the ultimate solution is a new computer or, as a stop-gap, "climb-the-mountain-that-is-linux" and dual-boot ubuntu 11.04.