Resetting Administrator’s password in Windows NT 4.0 can be done without using a third party software (either commercial or freeware).
If the file system is FAT16, all you need is a Windows 98 Startup disk.
1. Boot the computer with a Win98 Startup disk.
2. Navigate to C:\Winnt\System32
3. Rename file logon.scr to logon.old (Ren logon.scr logon.old)
4. Copy file cmd.exe to logon.scr. (Copy cmd.exe logon.scr)
5. Take out the 98 Startup disk.
6. Reboot the computer.
7. Wait 15 minutes and do not move mouse or KB in the mean time.
8. Instead of default Logon screen saver, Command prompt Windows will appear.
9. Type “MUSRMGR” without the quotes to start User Manager.
10. Change the Administrator’s password. Exit User Manager.
Step 9 and 10 may be replaced by "Net user Administrator xxxxxx" without the quotes,
where xxxxxx is a new password.
11. Copy logon.old back to logon.scr (Copy logon.old logon.scr)
12. Type “Exit” without the quotes to exit the Command prompt.
13. Logon Windows NT as Administrator with the new password.
If the files system is NTFS, you have two options.
Option1:
1. Connect your HD to a computer with Windows NT 4.0. If Service Pack 5 or later was installed, you may connect it to a Windows 2000 or XP computer. The file system must be NTFS.
2. Follow the above from Step 2. You navigate to X:\Winnt\system32, where X is the drive letter of your HD.
Option 2:
1. Install Windows NT 4.0 in a separate partition. If you have an unpartitioned space in your HD, create a partition and install Windows with NTFS there. Then follow the Step 2 of Option 1.
2. If you do not have unpartitioned space, you need a third party software (e.g. Partition Magic) to resize the partition, create a partition, and then install Windows there. Follow the step 2 of Option 1.
In Option 1, skip step 5. Turn off the computer, diconnect your HD, reconnect it to your computer, and boot the computer. Then follow the Step 7 thru 13.
Step 1 of Option 2, you boot to the Windows you just installed to make changes (Step 3 and 4). You boot to your original Windows to change the Administrator's password.
If your computer is a laptop, Option 1 may be a difficult one but doable.