I have an SSD with Windows 7 on it as a primary drive, and a secondary HDD with an old Windows XP install still on it. This system has been working fine for a few weeks, but suddenly the computer started booting up XP from the secondary drive.
The SSD doesn't seem to be broken, I could access all my files on it even when it was suddenly showing up as a secondary drive. When I unplug the HDD, the computer will boot from the SSD again, and when I plug it back in, it'll continue working fine for a few restarts, until it'll suddenly boot XP again.
Both drives are SATAS, and the SSD is plugged into port number 1. The only major thing I changed before the trouble started was turn off paging and indexing for the HDD.
What could be causing these problems?
ETA: After looking at the BIOS: At the times when it's booting wrong, the SSD doesn't appear in the list of drives at all, so it's not just a case of wrong boot order.