Dear fellow survivor. If you've been doing stressfull editing I think you can expect a limited system life span. A healthy power supply is probably urgently needed before anything is seriously damaged like your hard drive. The stress on the hard drive is also a concern. Even better, consider a new system in the near future.
I rechecked your post to see if you were using Aero but it is XP so that is not relevant. I never had a problem updating the BIOS with a 945WH board so there is no reason not to. Also XP probably has a limit of 2GB RAM so more than that is of questionable value. I don't blanket recommend Win 7 but for video editing it would seem to be a good idea. Two crashes in a year may not be bad if you are using multiple apps. Vista and Win 7 allow for more graceful closing of apps to avoid actual crashes. See TomsHardware.com for a discussion of memory management for graphics. You may be as well off with your system. The BIOS and INF should be reasonably up to date on any system, especially if you change hardware or update software.