When Windows won’t boot up, the natural course of action would be to start it in safe mode. When safe mode loads the drivers, and you see it hang up on “crcdisk.sys” there are several possible causes:

1) If the registry has become corrupt or changed and “crcdisk.sys” is trying to reference an entry there is a possibility that the             computer will no longer be able to start up and shut down correctly.

2) The second possibility is that the Crcdisk.sys file itself is corrupt.

3) If the computer has more than one OS installed on partitioned drives.

The easiest solution is to do a repair from the Recovery Console. Using the “fixboot” and “fixmbr” commands might resolve the problem. If not, you can use the OS disc to attempt a repair. If the issue is still not resolved you may have to do a System Restore.