I don't know whether it will fix your particular problem, but it might be worth trying the [Linux based] "NT Password Editor" [item 5 on the 1st menu when you boot from the CD] in the "Emergency Boot CD" [EBCD] below.
I believe it allows you to fix user passwords [and perhaps other user details].
1. How to make a free “Smart Boot Manager” floppy
This makes it easier to boot a chosen drive [particularly the one holding the EBCD].
2. How to make a free EBCD bootable CD
This has a number of useful utilities included including "Image" [for DOS, by Terabyte] & "File Manager".