I have a system running Windows XP Pro SP3. My wife is the primary user of this system, and the last several days in a row, when she tries to log in to the system it gives her a BSOD with the stop error code 0x000000F4. The rest of the error codes change every time she tries to log on, but that one seems to stay constant.

The error it gives me is:

A process or thread crucial to system operation has unexpectedly exited or been terminated.

The machine will also get stuck in a boot loop, where it keeps giving me the screen saying that windows did not start successfully, and to choose how to start windows. I have tried Safe Mode, Last known Good Config, and Normally, and all have resulted in either a return to the boot loop, or BSOD.

What might this mean? How can I fix it, without doing a clean install?