Sure enough, on the next reboot, it started doing the same thing my last Vista machine did - Failed to start, wanted to run the Restore service. And once you do that, it'll start to boot for several seconds, then crash. If you pull the battery and hold the power switch for a few seconds, then try again, it'll actually bring a screen up before crashing.
I know exactly what HP will tell me - reinstall the image that came with it (and then SP1, and then every patch known to mankind, and every app I've installed and then configured... Ergg!!!).
Time to look on the other USB drives and find the latest image, and reinforce the backup message throughout the family since it's my free time that gets eaten when these things crash.
Good grief, do I ever hate Vista.