My friends' pc is stuck in the cycle of booting to the:
-run in safe mode
-run in safe mode with command prompt
-last know good configuration
After choosing any option it restarts. the power unit was replaced recently, and it used to have 2 BIOS's but one died. Regularly the pc was crashing with the error of failed BIOS (or similar).
Windows xp (genuine) that was "built from different parts". (sorry can't be more detailed).