NT 4 Wks in continuous reboot

Has any experienced NT 4 Wks in a continuous reboot during AutoChk. On several occasions (different systems) if Chkdsk is set to run on the next startup, once the system reboots, chkdsk runs and then will restart and run again and ends up in a continuous loop with no way out. (Running SP 4, single processor).

Any ideas on the cause and any suggestions on getting out of the cycle without having to reinstall the OS?