This scam has been going for at least a couple of years now.

They used to regularly phone me but ever since I told them I was a programmer, and I knew exactly what was on my machine, they're stopped.

The bottom line is this: If a cold caller (someone you don't know personally) asks you to do anything to your computer, DON'T DO IT - EVER. Put the phone down.

If the call gets you worried about your machine, make sure your anti-malware software is up to date and run a full scan.

Phil