My hard drive is churning away (I can actually hear it - and the light is going crazy), but when I press Ctrl alt & Del, the task manager says nothing is on.

I have the most up to date Mcafee that tells me everything, but it doesn't see this.

What could be going on. What can't I see?

If its Windows Vista, its probably the Vista Search indexer indexing your hard drive to speed up finding files and folders.. it could also be other background tasks such as defrag etc.

if you are short on physical ram it could be the hard drive compensating by creating virtual memory

What spec andO/S is your computer and as mentioned, how much RAM have you got? Also how much free space is left on the hard drive? If it's full it will struggle. Download the demo of system mechanic and let it do what it wants, it's good at removing crap from your computer.

my pc is the same,always busy doing something:rolleyes:
and it has 93%free disc space,hardly running any programmes at all,a pain in the bum

It could also be the windows updates running in the background, is the cpu process running at a fairly high percentage, I find that the svchost process is updates from microsoft - but I may be wrong.

Since the advent of XP, Windows always seems to busy writing/reading the HDD. I had a look once using Sysinternals file and disc monitor utilities - constant drive activity but all connected with 'Services' and all seemingly legitimate.

The indexing service can be switched off - but if the HDD light is an irritation you can unplug the LED from the motherboard. I left it unplugged the last time I rebuilt this system.