Occasionally you may need to prevent a scheduled disk scan in Windows. This occurs during the reboot phase and can take a long time, sometimes even an hour or more depending on drive size and data contained on it. Once started it can't be stopped. Turning the power off can cause corruption to the hard drive.
Here's the answer to prevent it from occurring on restarting the PC:
Open the command prompt with administrative privileges (Type "cmd" in the search box in the Start Menu, then right click cmd.exe in the search results and select "Run as Administrator")
Type "chkntfs /x c:" (where c: is the drive letter of the hard drive you wanted to scan).
This will cancel the scan and allow a speedier reboot.