increasing the amount of physical memory in your computer would probably help the situation. 512mb is the bare minimum for windows and once it runs out of real memory it has to use virtual memory. (and it would make quite a speed difference to the computer)
I'd recommend fitting at least another 512mb of ram (or 1gb would be even better and hardly any more money)
there is a system scanner here that will tell you what type you need, don't buy it from here though, you can get it other places far cheaper.
http://www.crucial.com/systemscanner/