The status lights are saying you have a memory problem.  I would reseat the memory and then run an extensive memory test (memtest86+ is free and works better than the Dell memory test).

Memory errors can cause just about any symptom. 

Peter 

It's more likely a HDD problem.  F12 and run drive diagnostic.  That resides in BIOS so is not drive-dependent.  If it returns any error at all, the drive is failing and the sooner you replace it the more likely you will be able to recover all data.

It's somewhat remarkable that with all those things wrong with it, it still works at all.  I don't know enough about Windows' internal structure to be able to explain that.  But it sounds like many things are corrupt and the image will have to be completely reinstalled.  Don't bother until you've confirmed that the drive itself is sound, or you'll be doing again a week later. 

Viruses are much less an issue now that all email services filter for them.  Before they began doing that, there was at least one that could disable antivirus.  That McAfee shows but won't open, at least partly suggests you may have become infected.  But no known virus attacks the diagnostic partition, it's not even in Windows format, and that points more to drive failure.

Unfortunately, if you replace the drive, the utility of the restore partition is also lost and you will have to reinstall everything from CDs.  You might try restore (crtl-F11), but if the drive is failing, restoring it will not last, and in fact may not be possible. 

Doesn't hurt to check memory.  But with faulty memory, you wouldn't likely get anywhere near as far as you do (desktop, and consistent--albeit faulty--results).

Not to contradict, Peter.  But if you enter from BIOS (all the F commands) with an invalid boot resource, you do indeed get 123 on the lights, as BIOS doesn't find a valid source to which to hand off.  If BIOS offers the diagnostic partition, and the image has not been reformatted or repartitioned, yet the partition is inaccessable, impending drive failure is the likely cause.  As is the original problem which chkdsk/r "repaired".

What chkdsk can repair is extremely limited.  It can remove invalid entries, but it can't correct them back to what they originally were. 

I ran the drive diagnostic and both passed.  I assume it listed two because I have RAID.

I reseated the memory and there was no change when restarted.

I'm not sure I can run the memtest86+ because it appears to require burning to CD and that is not working.

Would disconnecting the primary (for lack of the proper term) HDD leaving only the RAID connected accomplish anything?  Isn't a HDD failure what RAID is supposed to protect me from? 

RAID 0 and 1 have almost no use, other than as marketing gimmicks.  RAID 0 can improve read performance by roughly 1/3, but at the cost of halving reliability.  ANY error on either disk renders the entire array useless.  And read time is not a notorious bottleneck in performance anyway.

RAID 1 hypothetically doubles reliability, but at the cost of halving storage space--you pay for twice what you get--great news if you're in the business of selling drives.

If a file is corrupted by an action of the OS or a virus, RAID won't help you at all.  RAID 1 can bail you out if a couple sectors on one drive become unreadable.  Thing being, sectors don't ordinarily become unreadable on their own.  I've had 2 drives for 10 years each, and neither developed unreadable sectors.  Unreadable sectors suddenly appearing is more typically an artifact of the drive coming apart internally.

Unless you reformatted/repartitioned/reinstalled at some point, almost the only credible explanation for the diagnostic partition being inaccessable is drive deterioration.  Very VERY few viruses target a single manufacturer's BIOS or their proprietary partitions.  The F12 diag should have caught that, but diags only look in certain places.  If those places contain no errors, the diag says "OK".  It can still be a drive problem.

But for now, try ctrl-F11 restore.  If a drive is failing, it will reoccur eventually.  If it is a virus, that should eliminate all traces of all but the most resilient and malicious viruses.  Hard to even imagine those propagating today, with all the filtering that takes place.  But anything can happen.

Thing is, just to boot and throw up the desktop takes almost all of the motherboard resources working properly.  That's why I lean away from that conclusion.   But again, anything can happen. 

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@x_lab rat wrote:

 

Unless you reformatted/repartitioned/reinstalled at some point, almost the only credible explanation for the diagnostic partition being inaccessable is drive deterioration.  

 

But for now, try ctrl-F11 restore.  If a drive is failing, it will reoccur eventually.  If it is a virus, that should eliminate all traces of all but the most resilient and malicious viruses.  

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I reinstalled XP about 10 months ago.

System Restore via System Tools is not available.  Does ctrl-F11 do the same thing?  I am reluctant to do anything that will cause me to lose data.  It's all still here right now, I just haven't figured a way to back it up.

Ctrl-F11 restores the system to exactly the same condition as when you took it out of the box. All programs and data stored since then will be obliterated. Backup would be problematic if you can't access the CD writer, or at least the floppy (if so equipped).

The reinstallation may have obliterated the diagnostic partition. If it did, there's a good chance it obliterated the restore partition as well. I don't know the exact interaction of these components, given user intervention.

Windows 'restore' is not the same thing as ctrl-F11 restore. Given that you can't access IE within Windows, I'm not at all suprised you can't access Windows restore either.

Given an image that would not respond or repair, I would wipe it and reinstall from scratch after somehow backing up that data which I wished to retain. It may take buying a USB floppy and a box of discs. And I'd probably turn off RAID in BIOS, and use the other drive as D: for file storage.

As an engineer, I would never use RAID in an enduser system.  RAID 0 is nothing but a liability, and RAID 1 is not a safeguard against OS corruption, which it seems you have suffered. 

I will display some more of my ignorance.

It is not certain, although suspect, that a failing HDD is the root of my problems.  Could I remove the drive from my computer and install it as a second drive in another?  

Could I determine if it is bad that way?   

If I didn't try to boot with the suspect HDD would it corrupt the host computer if, indeed, the HDD is failing?

Is it possible, even if the drive is failing, that I could transfer my files from it to the host? 

If I replaced the host HDD with the suspect one, booted the computer, and it showed the same problems I'm having with my computer, would that be a permanent problem in that computer or would reinstalling the original good HDD fix it?

I believe I have RAID 1 i.e. 2 identical hard drives.  

So how about this?

I physically unplug the data and/or power cable from SATA 0.  Would the computer then be able to boot from SATA 2?  

Is Win XP even on SATA 2 and, if so, if it is corrupted on SATA 0 will it also be corrupted on SATA 2? 

In RAID 1, both drives contain the same information.  'Everything is everywhere', the OS, the data, and unfortunately, if corrupt, the corruption.

I don't know what the result of running only 1 drive of an array would be.  It might hang the RAID BIOS, looking for the other drive when it's expecting to see 2, even if one won't read.  Hypothetically, you should be able to plug in another blank drive, and after quite some time RAID would rebuild the contents of the remaining drive onto the new one.

But at this point, that wouldn't solve anything.  The same erroneous data is on both drives, and would get duplicated onto the new one.  Plus we don't have a positive indication either drive is bad, just an unsupported hypothesis. We do know that something caused the errors that chkdsk 'fixed', but that could have been anything--faulty read, faulty write, software run amok, either accidentally or deliberately, even RAID's interpretation of which disk was wrong and what to do about it.

In any case, you cannot take one drive of a RAID array and plug it into another computer, whether it supports RAID or not.  The drive contents are ID tagged to match each other, and to match the RAID BIOS which created them.  You could move BOTH drives to another RAID system that used the identical chipset.  But once RAID is created, it's fairly xenophobic.  Even RAID BIOS revisions can be incompatible.  However, if you had an identical system which worked right, moved both drives to it and it then did what the original one does, you'd know unequivocally that the image is faulty.  How it got that way is still a matter of speculation.  You might not want to try a good image in the faulty system.  If there is actually a hardware fault, it could corrupt the working image.  (I've had bad motherboards destroy known-good images before.)