The command to set a password to blank is simply this:
net user username ""
Execute it in a Command Prompt (cmd) that is Run as Administrator.
Note: There’s a nice vbs script that tests which account has a blank password here.
net user <username> /passwordreq:no in an command prompt opened under the Administrator account’s context (In Win XP hold down shift and right click on cmd.exe to Open as another user, then enter in the “Administrator” account’s password; Win Vista+ just right click and select Run as Administrator). Then run
net user <username> <password>
This has the advantage over
net user <username> "" that it allows one to change the user in question’s password from something to nothing, in
lusrmgr.msc and other GUI user management tools, as well as using the
net user command in future.
NOTE: Yes, this is very similar to jordyonrust‘s answer as I haven’t had much success with editing other’s answers to correct minor mistakes/omissions (the latter more often when I need to make more than a couple of character changes to correct a mistake and the additional information “changes the intent of the answer too much”).
net user <username> passwordreq:[yes or no]
Used to determine if the account needs a password. Not sure it works. Maybe this will do?
You also might find this interesting: Net.exe reference
the command is
net user USERNAME PASSWORD
if you leave the password blank it may remove the password, however I have a minimum password policy on this machine and I cant set a password with 0 characters