I’ve now seen this problem twice in 1 month (once on a laptop, and once on a desktop):
XP won’t start (windows splash screen with rolling bar at the bottom, then it just restarts (with no blue screen).
I run bartPE and mepis, but they say the HDD partition is either “raw” or “unknown”.
In both cases, I’ve had no other option but to do a fresh installation of XP.
The only thing common between these PCs, is that they both were badly infected at some point in the past.
Its quite mysterious, and I’d like to know what happened (particularly if it starts happening more often).