Normally I don't support stand-alone / home PCs, but there are about half a
dozen people who I give ad-hoc support to on their home PCs. Two of them
brought their computers round to me on Monday beacause they've got problems.
Progress, at present is very slowand I'm not sure which of the similarities
between the two systems are relevant clues and which are red herrings.

Both PC are recent Lenovo machines with Vista Business (SP1) and F-Secure
Internet Security.
The first machine is used primarily a "the family PC" in a non-techy
household. The potential for malware is high. Description of the problem and
events leading up to it are vague and confused.
The other machine is a home-office machine, used for general office
applications and photo editing/filing. User is quite careful about intenet
usage and leaves the machine on overnight every Friday night for F-Secure to
carry out a full system scan. It was noted on Saturday morning that the PC
had rebooted and the problem started then. It appears that several
patcheswere installed overnight. I've manually uninstalled the windows

The sysmptoms are. The PCs are VERY slow at start up and after logging on.
There is almost constant disk access. Task manager is slow to respond,
sometimes crashes, but doesn't show a great deal of activity. Problem is
also there when booting in safe mode, though not to the same degree. Booted
from UBCD4Win and ran various anti-virus anti-malware scans but nothing much
more than some tracking cookies were discovered. Windows Explorer hangs.
I've tried disabling F-Secure but not much difference.
Neither machine has any restore points saved though neither of the users can
recall disabling auto restorepoint creation. When I am able to get
performance monitor to load it doesn't reveal anything much. (e.g. Windows
sidebar using 47% cpu, but machine still slow if sidebar disabled -too slow
to get performance monitor to load!)

Any thoughts other than FDISK?