LSASS Error

Hi,

This weekend I played fix a PC with this famous error message LSASS service. I don,t know much about it, but I think it is related to a virus, and I would like to know if anyone knows a way to fix it without formatting the pc. Can we access the registry without boot, something like that another option ...
Any ideas about this?

Well, as you say whether or not it works with boots

Safe Mode in any way / manner

Then you have only or
Reinstall or Xp
Repair

First test using :

Kaspersky Rescue Disk