My wife's laptop has Windows XP pre-installed. Every once in a while, the loading bars just go round and round, and bootup proceeds no further. It has just been overhauled by the dealer, who took out old backups, etc. Since it has a pushbutton power switch, I need to disconnect the battery to reboot. I then go into "last working setup" and it boots, but it fails again on the next bootup. I have tried rebooting step by step from Safe Mode without a permanent fix. I now use Linux, so I may have missed something? Doug.

If it only hangs on a normal boot, you can boot with logging enabled. Once you know it's hung, press + hold the power button for approx. 10 seconds. Boot again into safe mode and look at the log; the last line should be the problem driver/service.

Thanks. I will do that and report back. Now that I have this knowledge, it probably won't misbehave. It didn't just now.

It just misbehaved again. Holding down the Power button, it shut down in about 4 seconds. On rebooting, I looked at all logs I could find without any clues. Didn't see "boot.log" Is it generated automatically when I boot into Safe Mode?

You have to attempt to get a log of the crash, which is one of the options from the boot loader menu. This, of course, requires you to either select it on every boot, or have the problem occur twice in a row: once so you know there's a problem, then again with the boot logging turned on. There IS a way to have Windows always log the boot, but I haven't posted that because it's one of those things where a mistake will cost you your ability to boot.