Win XP Drive Errors Every Boot

Does this sound familiar to anyone???

For the last few days I've been getting strange behaviour on my Win XP Home
system (NTFS disk), in particular, multiple file system errors EVERY time I
boot up.

For a while Windows would step in and try to fix them with CHKDSK during
boot.

This no longer happens but if I run Norton Disk Doctor straight after boot
it ALWAYS reports errors in the Security descriptorss section of my boot
drive.

It will ALWAYS say there are errors in the volume bitmap. it also
intermittently shows up a whole bunch of errors in other sections of the
test, including:
Corrupt attribute records
Index errors
Orphaned files (143 orphans earlier today all from one directory file)

(Surface test always reports OK and no errors show up in the file data area.)

Errors are ALWAYS found on the boot drive but often also on other drives,
including my empty and unused drive G. I should note that drives C: to G: are
all on one physical disk.

I've also twice had Windows report itself unable to boot due to a corrupt or
missing system file (windows\system32\config\system)- fixed with a boot from
the installation disk and "R".

And the system clock has started losing hours.

And the other evening, during a session where the computer had been working
OK, the computer stopped running most of my software except Windows Explorer
and Internet Explorer. However after running Norton Disk Doctor from their
recovery disk the problem seemed to go away.

To eliminate or define the problem I have already:
- Done thorough hardware tests using the disk manufacturer's software.
- Done full virus scans with Norton's latest updates.
- Moved my whole system to a different physical drive.

And it all still happens.

There have been a couple of error messages on boot to say there have been
serious errors due to a device driver but when I check all devices are said
to be working properly. And no device drivers were added recently.

The only thing I did do before all this started happening was run the Norton
System Optimizer, the only changes i made were:
1) I checked the box to disable NTFS last access time (to speed up disk acess)
2) I adjusted the mouse wheel scroll rate.
I have returned both of these settings to their original condition.

Any suggestions?
--
Mark H