COMPUTOR GURU'S HELP

[MadaMaoriJR]

Hi everyone I desperitly need some help badly

Today while running SBYBOT-search&destroy in the middle of its test, it came up with 'yr computor needs to reboot at end of scan' , so i let the scan run and it rebooted

Now the problem!
When i start the comp normaly it gets the the desktop and plays the wellcome sound but no icons or start button appears then it shuts down and go's to user accounts page/window with only my name there.
So i try in SAFE mode, It dose the same thing so to speak( brings up the 4safemode thing in the corners) then drops back to users screen, BUT this time there's admin and my name there(never had this before ) clicking on either name dose the same thing, logs on for a millasecond then go's back to user's screen again.
Even useing Last Known Good Configuration it still drops back to users screen.

Anybody have any clues?

Cheers MMJ