I installed Windows 7 RC. When ever I am booted into Win7 one of my hard drives (probably not system drive - sounds like my secondary storage drive) is constantly working. Not very much but still making sounds.

I have completely turned off indexation, there is no automatic defrag going on. I have set a constant size to the paging file and there is no antivirus activity going on. The hard drive is making noise even when the system is idle for a long time and also when I am using it.

The processes tab in the task monitor shows no process that is using CPU.

What can this hard drive activity be?