From: John Beckett 

"Dave Ings"  wrote in message
news::
> There is some process doing disk I/O every 5-10 seconds even when the
> machine is idle.

At following you can find diskmon and filemon:
http://www.microsoft.com/technet/sysinternals/default.mspx

First give the logs in Event Viewer a thorough check.

On some older systems, I had similar disk activity that was due to having
RAS (Remote Access Service on a server) running while configured to answer
an incoming phone call via modem, but the modem was switched off. You could
check Network Connections to see if anything looks like it might do
something similar.

John

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