I've had problems on two different laptops after using Defraggler 2.08 and setting it to shutdown when the defrag operation is completed. I left it running overnight, so I wasn't there when it shut down.
In one case it just looked like a minor problem in the registry, with a folder in Program Files opening at startup.
In the other case, it was a complete show-stopper. Registry files reported as missing or corrupt, and Windows unable to start. After patching that, I got a corrupted hal.dll message.
These look typical symptoms of a premature shutdown. Fan ducting was cleaned a few months ago, and I have no reason to suspect a thermal shutdown, and it's a laptop with a good battery, so it couldn't be a power cut.
Anyone else had any similar problems?