I've often noticed that sometimes my boot hard disk goes crazy, disk
activity light flickers constantly, system becomes unresponsive, but
there's no particular process hogging the processor cores. I managed to
watch one such incident while Hard Disk Sentinel was present in memory,
and when I looked at the boot disk in the Performance tab, it showed
100% activity, but data transfer was down near zero. Obviously, I had to
reboot the computer to get it back to normal.

I'm talking about Windows 7 Ultimate 64-bit in this case, but I've seen
similar things happen under Windows XP Pro 32-bit in the past too.
Another thing I noticed is that during this time, the System's own
SVCHOST.EXE program is using up a lot of memory too, over 300MB by itself!

What could be happening here?

Yousuf Khan