Thanks, the noise is not constant, I'm sat on the computer now, it's not happening all the time, it'll do it for a few seconds, then stop for a while, then it will do it for a few seconds and stop again, I'm tempted to test it by the methods you've both suggested, but I don't have a working drive big enough to back up my data as my last one was about to fail and I removed it to keep the data I had at the time safe as a last resort if it all went pear shaped, I keep meaning to buy a usb back up drive, but first I bought more RAM, then I bought a new monitor, possibly a silly mistake, but I just couldn't resist the immediate benefits I would get from the upgrades I got, I have two drives, but while writing this I just realised one of my drives isn't showing up, just looked and I haven't reconnected the power cord on the second drive which I use for xp, so does that mean it's the main Windows 7 drive?