Windows

The best way is to go to http://www.l0pht.com/ (note that's a zero not an o) Then down load their password cracking program.

Hi, take a look at:
http://www.pwcrack.com/
For nt server, you'll be sent to another link (I looked at password.com)which shows you your options. Hope this helps.

or, if you don't care what the password is, you canreset it using ERDCommander from www.sysinternals .com

if you can access the NT dir from a floppy disk(if it's FAT) or from another network computer or WINNT installed in another directory, just rename the file "logon.scr" to cmd.exe . restart your computer and DO NOT touch the KB/MOUSE for atl least 15minutes.
the screan saver will be "CMD prompt" !!!
type in the command line "usermgr"
and reset/change what ever you want

if you can access the NT dir from a floppy disk(if it's FAT) or from another network computer or WINNT installed in another directory, just rename the file "logon.scr" to cmd.exe . restart your computer and DO NOT touch the KB/MOUSE for at least 15 minutes.
the screan saver will be "CMD prompt" !!!
type in the command line "usermgr"
and reset/change what ever you want