I've been running Win7 for a few weeks now on my Sony Vaio laptop. No problem. I went into the user account control area and reset the account control to the minimal setting. It asked for a reboot. Upon reboot the system is completely black screen with no HD activity. I can't boot from the CD. The CD spins up but then stops. It looks like a BIOS scramble. I am totally stuck and ticked off. Suggestions? This is a Sony Vaio VGN-T91S. I am unable to use the F key to get to the bios setup. Interesting to hear the CD working for about 10 sec or so then stop. The most I get is a blinking cursor in the top left corner of a black screen. I never get to the Vaio logo.