I recently cleaned out (reformated one partition) one of the 2 harddrives.
(reason: suspected virus activity causing system instability and strange

Upon reinstalling XP pro I added Service Pack 1&2.

The problem I now have is that the pc 'deactivates' (meaning that it
randomly and apparantly 'does nothing'.). It can be five seconds between
those times of 'doing nothing' and up to over one minut. The time span of
'doing nothing' is about one second.
Immediately after the 'doing nothing' - and for less than a second - the CPU
usage soars (Win Task manager) up to about 70% and then settles down again
to whatever it was before, say 2 or 5 %.

I must add that this strange behaviour does not appear to be associated with
or dependent upon any additional programmes running or not. But it does
appear to be activated by just about any activity - even just moving the
mouse cursor across the screen (It just gets stck and reappears somewhere
else on the screen).

This problem is quite unacceptable, especially playing music or watching a
movie (DVD or whatever), then the process halts for the second that it
takes. Otherwise it is just annoying.

Any clues? I would be most thankful for help on this.