If the system boot drive C: is fat 32 not NTFS and you can boot from floppy A: boot up useing floopy, goto CD C:\winnt\system32\config
del sam
sam is you password file.
reboot and login using default administrator and blank password.
if system is NTFS you can still fix but will have to use and program called NTFSDOS to boot with.
ben there and done that, good luck.