I wouldnt buy a PC just yet, you have a 2.4ghz processor which is more than adequate if all you want to do is browse then net, view photos taken on a digital camera etc.. I would personally buy some extra ram(£40) as with only 256mb you have the bare minimum.

Another thing not mentioned is that you may have a virus and spyware on your pc. If you go to this link and download this program, install and use it to check your pc.

http://www.download.com/3000-2144-10045910.html

If you can also press the control, alt and delete keys together a window will pop up, click the performance tab at the top and it will tell you what free memory you have.