Constant HD Activity

I upgraded from Vista to W7 Home Premium about 3 months ago and in the last few weeks my PC is showing constant HD activity (not flickering, on permanently). This causes all programs to regularly show "not responding" for up to a minute before coming back. Everything is very very slow. My PC is a Dell precision 490 with dual processors so should be fast. Two 500Gb HD's, one for OS only. Both have plenty of space available.

I have checked defragmentation on the C: drive and this is 0% (runs every week).

I have turned off all I know but even with no applications running the disk light just keeps on going....help!!

Any suggestions?

C

Thanks, I did all that but when I open the performance tab I get CPU usage & Memory but no "disk tab"....am I in the wrong place?

I get "resource monitor" button at the bottom

C

Opened resource monitor and found the disk section. Looks like "memopal crawler" is causing the issue (online backup program)...won't let me stop the service there so I will try to stop it in start up and go from there

Thanks