Just to get rid of the obvious, is your keyboard clear / clean? Something resting on a key can produce beep sequences.
The other things to check are that your fans are working ok - if your BIOS is set to monitor the fan speed, this could be the cause of the beeps.
Also try removing and re-seating your graphics card.
The other options relate to failure to enter / recover from power-saving mode, but as you were surfing at the time (even though this site does get really slow at times), it is unlikely that this was the cause :)
Thanks everyone for taking the trouble to reply. I have had NO BOTHER whatsoever with the computer, and everything is running fine. The machine has not been moved an inch since installation, so I very much doubt that anything is loose. Touching two keys at once on the keyboard does make sense, as I try to rush things, and can get clumsy. As a matter of interest the keyboard is part of a TRUST keyboard and mouse wireless set. I will close this posting now, I was just curious.
Incidently the computer so far has proved me to be 100% right in going to my local shop. I could not be more pleased.
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