If you install a new driver or service and its corrupted or incompatible, at reboot the new driver or service may make Windows NT so unstable that it fails before you can logon and disable it. Its a catch-22 gotcha! You need to logon to disable the service or driver, but you can't logon because the defective service or drivers causes Windows NT to BSOD or reboot too early.

The only way to break of of the catch-22 is to cheat. You have to install a 2nd version of NT and disable the defective service or driver. Boot using this backdoor version and use regedt32 to disable the problem driver or service of the offline version of NT. When people first hear this approach, they wonder why it would work - after all, when regedt32 opens, wouldn't you be working with the hive of the 2nd install? What you do is load the system file hive from the offline problem version of NT, found on most installs at %SystemRootOfFailedNT%\System32\Config\System . Once the system hive is loaded, you can modify it and save it back. I have loaded hives from the ERD for similar purposes but this is actually less drastic. You are disabling a single service or driver. Microsoft kb article Q165748 gives detailed instructions.

If the problem is caused by a service pack installation or removal, if you have the appropriate ERD, you can resolve the problem by booting NT installation disks or CD and selecting a repair of NT executables.

ERD Related Tips:

• NT ERD - never there when you need it
• Contents of NT ERD
• Steps Performed by the Emergency Repair Disk
• Disable a Service or Device that Prevents Windows NT from Booting
• Cracking Windows NT passwords
• Using the Emergency Repair Disk to Fix Windows NT Problems
• Repair Disk Secrets Reduce Downtime
• Patch Available for RDISK Registry Enumeration File" Vulnerability