Install BSOD, computer won't boot

I tried to install Avast free edition on my aunts computer and when it was almost done installing, the bsod popped up (windows vista). The computer turned off, and now every time I turn the computer on, the screen stays blank. Has anyone encountered this problem?
Its a compaq laptop, with windows vista installed from the factory.

what AV was installed before you installed avast! ?..compac usually comes with Norton preinstalled
did you remove it before installing avast! ?

can you start in safe mode ?

If you can, then try uninstalling avast with the removal tool
Then run a removal tool for the installed or previous installed AV reboot and try again

Uninstall Utility http://www.avast.com/en-no/uninstall-utility
uninstaller tools http://uninstallers.blogspot.com/