M Brian

i think a fan is gone on my PC its rattling its little bag off when i start it up... sometimes it overheats and shuts down meaning I have to pull the power lead out of it before it will turn back on at the switch..

there are a few fans on it when ive had the case off??

which one is it most likely to be and how do i go about changing them and where best to get them from?

Eagle

iTrader: (2)

sounds like the one on the processor (one on the main board)

hate to say it but pcworld might be the easiest .. deffo try a local computer shop first ..
normally screwed to the heatsink ... could be easier to get a complete new heatsink and fan..