Isass.exe stops xp from starting HELP

ok I have a laptop that wont start. Details:

ERROR: windows xp will not start at all, I have tried everything I know of as below. after the black xp screen with the green bar, a box apperas saying “Isass.exe System error , Object name not found” , and when u close it, the pc restarts.

xp home sp1
I have tried……….
F8 – all the options like last good and safe etc
recovery console – tried chkdsk etc etc , tried to locate the .exe file to delete it but cant get to it

Its actualy not my pc, the last guy also tried to reload windows on top, so also when u start before the error appears it comes up with restarting windoes setup, then skips to the error.

ANY HELP would be muchly appreciated !!!

Cheers

Mark