Doesn't sound good!
The IRQL_NOT_LESS_OR_EQUAL Stop message may indicate which driver is causing the stop - do you get a stack dump on screen?
Anyway, if this only happens in Safe mode, my guess would be the standard VGA driver - it's the obvious difference between Safe and standard mode.
Suggestions would be trying to reinstall SP1 (if you've still got it) or using the Recovery disk to reload the standard drivers (Info on MS KB website on how to do this). If these fail, you'll probably either have to hope you don't need safe mode or go for the dreaded reinstall

.
Sorry I can't be more hopeful.
Steve
MCSE (expired

)