This is not unusual at all, and there is simple explanation: Your disk is over 128 MB, and Windows version can not handle it correct. When some data goes on part of disk over 128 GB it will go actually to begin of drive. Correct place - 128 MB is formula where goes. SP1 for Win XP fixes that problem.
i'm thinking maybe all the discs are ripped to the same folder and share the same VTS_01_blah structure. bits might have got overwritten, and other bits might not have depending on the sizes of the discs used and their file structures. i know .IFO files are fairly robust, and can be made to point to completely different files and still play back okay in some decoders. but we'll need more information than that. @ didee: that doesn't make sense - isn't Quantum Knot currently tuning Vorbis? where would he find the time to drill holes in the universe?
Since Daniel hasn't returned, we really don't know what the root cause of his trouble was. I suspect that he'd turned his PC on it's side, and all the bytes fell off the disk.
I figure he waxed the wrong side of the computer, and ate the chicken after sacrificing it. That's a major no-no - the gods don't like you eating their sacrifice.