Why does my computer sound like it's try to post every 5 mins in Vista?

[timmins]

It's weird and starting to really annoy me, but randomly makes a small kinda beep from inside the tower, then sounds like its kinda boosting up.

Seems to sometimes tie in with a new winamp song, causing maybe half a second jolt. Any idea what it could be?

 

[timmins]

Thanks buddy, much appreciated> it's changed now (was on 20 mins) so hopefully does the trick.