Hmm.....Try continually pressing F8 when you first boot as sometimes, depending on the set-up, it can be hard to 'catch'.. Then if you get to the options screen choose 'safe-mode' and un-install the update.

Or... If you can get into the bios (and have an install disk), set the boot order to boot from CD/DVD, save the settings, place your disk in the drive and then reboot. You should now be able to enter the install options which one of these is an option to repair. You could just go for the repair and hope it fixes the problem or a totally new install which obviously means you'll lose any saved data...

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