lsass.exe error-computer won't start up?

Hi all

I can't boot into safe mode or last known good configuration,it just keeps restarting with the same error message about the lsass.exe and something about a password...any ideas or is the laptop dead? My other machine is working well...so I can't assume the latest microsoft updates messed it up?...or perhaps the kids or perhaps it has just had it's last breath and it's time to say goodbye...:smileysad:

Can viruses do this stop the lsass.exe working? I sort of know it is a major part of the XP system but that is the limit of my knowledge.

Any help most appreciated or any thoughts.