At intervals of about 1 minute I hear a musical bleep bleep coming from my PC. I had a look around and when I looked in Administrative Tools in Control Panel I found a continuous line of errors in Applications occurring every time I heard the bleeps.
I googled " CWF Tracker Event 109" which was the fault indicated and was totally bamboozled with the info given.
Thank you both for your replies and sorry for the delay in getting back. I've still no idea what it was but it has stopped now. My PC is a Compaq so I'll look at their website for aclue. Thanks again lads, I'll click as resolved.