Sounds to me like it will be the power supply, this usually fails like this to start with. Have a look at what output it is, normally 400 or 500 Watts. I would take it out of the PC, it's not that hard, 4 screws and then take the connectors out, take it to your local computer shop or Maplin if there is one near. You should be able to pick one up for about £25 - £30. You could ask if you could take it back if it doesn't fix the problem but 9/10 it does.
Hope this helps.
Martin., August 2007
