That does sound pretty bad - I have used Firefox on many machines for quite a few years, and never ever experienced it - or any other browser - causing a hard reset.

Basically I see only 3 possible causes for this;

1. malicious software lurking in your system and trying to protect itself from removal (or a very faulty security program)
2. a hardware problem - a (possibly serious) harddisk error could cause such behaviour, or (less likely but maybe possible) a faulty RAM block, network card or system board.
3. an error in a critical windows system file (not very likely with your description, but slightly possible)

To address first possibility, please read and follow the suggestions in this article: Troubleshoot Firefox issues caused by malware - if malicious software is found on the system, it is most likely the cause, and you should be able to clean out the system with the tools found from the links in this KB document.

To test your harddrive, open My Computer and locate the drive icon for the drive on which the crash-causing Firefox was installed, most likely drive C:. Rightclick it, select Properties, and click on tab Functions. The top button on this page should be the Windows Scandisk tool - click it to make Windows look for errors on the drive, and restart your system to allow Windows to make a complete scanning of the harddisk during startup. Do not interrupt it while it scans. This should locate faulty sectors on the disk, if any. You can find additional tools for diagnosing harddisks in this guide, step 4 if needed - and further down the same page you can find tools to test RAM and other tools that may help with Windows or hardware problems.

Please let us know how above works out, and if we can be of further assistance. Detailed feedback is appreciated and helps us to help you better, plus enables us to better help other users with similar issues.

I believe it is none of the above. My system is running just fine now, the only residue of the problem is that I have a folder named "Oorklkcl.default" in my recycle bin that I cannot remove without having my system cold-restart. I have an up-to-date iolo antivirus program, a fresh Firefox 3.6.3 install, and pretty much nothing else on this computer, as it is my dedicated internet machine. That "Oorklkck" folder in my recycle bin is like a wart- it's not doing any damage, but it's annoying that it's there.

Okay, I did something wrong when I tried to preview the above message. Oh, well. Antivirus finds nothing, anti-malware programs ditto, hard drive okay, memory okay. No symptoms now, no real effect except for that one folder in my recycle bin that won't let me delete it. What is the Oorklck.default folder, anyway?

Oorklkck.default is a Firefox Profile folder. I have never heard of anything like that happening, either, when trying to delete a Profile folder from the Recycle Bin on Windows.

If that did happen to me I would Restore that folder from the Recycle Bin, and then open that Profile folder and start to delete the individual files and folder in the Profile folder to try to discover exactly which item was causing Windows to crash. I would also turn off that auto-restart for OS crashes, allow the BSOD and codes to appear to get the error codes for a crash like to figure out what was happening.

WinXP: Right click on My Computer > Left Click on Properties> Left Click on Advanced > Under Startup & Recovery> Click on Settings>Uncheck Automatically Restart > Click OK > Restart