I check Task Manager Performance graphs for the following:

1 - RAM = 16>32

2 - THREADS = 2

This gives me a nice 100% usage.

whew!
 

OK, so I reinstalled Windows and applied all available updates, and my system seems to be running 1000% better. I rendered the vegas project with no major speed issues. I'm thinking that there was and/or had been a major security problem that had gummed up the works. Things seem to be OK now.

I'm still going to clean around my fans, though. Thanks, Graham.

Glad you got it to work. It sucks to spend 5 hours rendering something only for it to die or crash.

Back-up your registry now for future "sanity" checks!
 

Now that you've installed a clean instance of Windows XP with your base applications, back-up your registry! If you run into future crazy behavior, you can quickly restore your registry back to sanity:

http://www.windowsnetworking.com/art...ry-Backup.html

If restoring a clean registry doesn't resolve things, then a re-install would be the next logical step. A full OS install doesn't take that long, especially if you have a dedicated "system" drive with just a few applications, keeping your data on some other disk. It's often easier to simply re-install rather than spend hours trying to resolve the enigma...