This seems like a really simple problem to resolve but I'm having trouble with it. I've got a PC that has XP on it. The video card failed in such a way that it's still usable, but annoying. (It stopped sending a red signal to the monitor, but green and blue still work) So I replaced the video card with one from my computer junk cabinet, and sure enough.. back to RGB again. BUT.. I can't get the stupid thing to boot into windows now! Not even into safe mode. It starts loading drivers, and then just crashes.

In W9X, the computer would boot up using a generic VGA driver in this situation, and you'd be able to select the proper driver and reboot. In XP however, no luck.

What do I need to do? (other than find an exact replacement for this obscure video card? :) I thought about just re-installing XP, but I would rather not lose all the installed apps and have to re-install everthing. Surely there must be a way to force it to boot up in "basic VGA" mode.

Try starting up from the installationCD and repair Windows from there.... This is possible unlless you have a repair CD with only the image of the basic installation of your PC. Also check the BIOS for possible PNP settings and errors.

I never tried the repaid option.. I will see what happens. What would be nice is something like the "detect new hardware" function in control panel, so that windows could determine by itself what driver is needed. I'd be happy if it would just let me give it the river of my choosing, though!

If the old card still works, put it back in. Then boot Windows and delete it from the Device Manager in the System control panel. Once all drivers for the video card are removed, shut down, switch cards, and reboot. That should be enough to get it to use the standard VGA driver temporarily.

If the PC still does not boot you may need to uninstall the drivers in control panel, add or remove software.
The PC should then boot with default video and find your new video card.
Good Luck