Computer drops into idle (C1) state for 1 to 2 seconds, then recovers

Hi,

My computer has been appearing to freeze for 1 to 2 seconds. Investigation reveals:-

1. Disk queue length for Seagate drive (platter) goes to 1 or 2 at start of event, and stays there for duration
2. Disk I/O for Seagate drive ceases completely during event
3. CPU enters C1 state
4. CPU core voltage drops to 0.8V (part of being in C1 state)
5. VCC stable
6. CPU temperature stable and well within limits
7. CPU Interrupt time drops to zero
8. Graphics card goes into idle (even if it happens in the middle of a graphics intensive game)

Tests so far:-

1. chkdsk - all ok
2. Intel processor diagnostic - all ok
3. Seagate diagnostic tools - all ok except if the event occurs during the test, then the program itself crashes and doesn't give a result
4. Hardware monitoring - all ok
5. Ran perfmon through a couple of the events, reported OK

I am having trouble separating cause and effect. It is as if the system, no matter how busy it is, just decides to have a sleep for a couple of seconds. I initially suspected hard disk, but that could just be a symptom.

All has been fine for 2 years up until a month or so ago, system is 2 years old.

Any thoughts?

Fixed. Took a punt, cloned and replaced the Seagate hard drive - all is now as good as new. Not enough wrong with it to fail chkdsk obviously, but enough to create instability.

Cheers