If you have a computer that is running Windows 7 or Windows Server 2008 R2, which crashes during the startup process before you are prompted for user credentials, then this article may interest you.
In addition, you may also receive the following Stop Error message or Blue Screen Of Death:
STOP: 0x0000006B (Parameter1, Parameter2, Parameter3, Parameter4) PROCESS1_INITIALIZATION_FAILED
This occurs because the Bootcat.cache file, located at %SystemRoot%\system32\codeintegrity, is corrupted or because the size of the Bootcat.cache file is changed since the last successful start.
To work around this issue, start the computer from the disc drive or from the USB drive by using the Windows installation media. Delete the Bootcat.cache file, and then restart the computer.
Microsoft has also released Fix314438 to address this issue.
Visit: Microsoft KB981833 to download the hotfix and for more details.
Windows Info Portal 
Posted by hstapel on November 27, 2010 at 12:11 am
I had this problem. This fix poses 1 question: how to apply a hotfix to a system that doesn’t boot…. anyone?
Posted by Obinna O'sobalu on November 29, 2010 at 12:54 pm
Actually. I don’t think you can. But maybe someone has a different opinion.