I found that on these scenarios if you ensure that the CPU keeps cool it helps A LOT!
Try re pasting the CPU with some fresh decent Thermal compound and maybe even upgrade the heatsink/fan for a nice meaty one, they are only a few quid…and then make sure you got some decent case fans…..
Also make sure you blow or hoover out all the "furry" dust build up.
And obviously make sure you don’t have any unnecessary programs running in the background on the PC…look at Task Manager to see what’s running. A clean XP install is also a good idea if the PC has been used previously for day to day usage.
I had a PC that would "fall over" after a few days of continuous usage and it would start skipping like you said and then after doing some of the things I’ve just mentioned, it would run for weeks or months without a problem.
If this doesn’t help then I’m afraid it’s about time you went (at least!) dual core…. you could build a decent one these days with all bells and whistles for less than £300!!!
God Luck. 😀