Donna's computer crashed today coming out of hibernation mode, and upon reboot it displayed an "lsass.exe - System Error, Object Name not found" error, then rebooted again - in a continual loop. I tried a number of different things, but what finally solved it was to follow the directions in this article: "Windows XP Crashed? Here's Help"
by Charles White. Basically, the article walks you through using your system restore files to set the system back to a previous save point, but it does it via the command prompt in the Windows Recovery Console mode - and if you can't get Windows to load because its corrupted, this may be your best option. You still need a bootable Windows XP CD to get into the Recovery Console, but the article does a great job of hand-holding you through the process, and I think this can be used to solve a whole slew of otherwise-intractable problems.
I'm sure if I'd taken this to Best Buy, they'd have charged me hundreds of dollars, told me the system was a write-off, and reformatted the whole computer. Instead, using White's directions, the computer is working again good-as-before in a couple of hours - and most of that was finding the article online, once I figured out that was what I needed, the actual process took less than a half-hour. A valuable find!