xp professional not logging on

Good Day to all of You
One of my friend's laptop loaded with Win XP (P), he says it not allowing him to log on when ever he tries to log on, instead it log off always by showing saving settings, pls help to resolve this issue.
Thanks
Raneesh

 

Can he logon as Administrator ?

 

dear friend
its not allowing through administrator too, its showing the same thing savings the settings and logging off for administrator too, i tried last known working settings, even in safe mode also its not logging.

 

I believe I had this problem awhile ago. Did he delete a system file by any chance? I guess system restore is out of the option.

Try last known good configuration.

 

no i didn't delete any system files, it was working, all of a sudden it started responding like this, previously it was showing system.exe error when it boots to xp desktop, when i click close button, its getting closed,during that time i had checked the startup option and all, but i could not resolve it