What can I do if I forgot my Windows password?
The adminstrator account was disabled and all that is left is the "other user" (as it calls it).
How can I gain access to the computer?
I would use Trinity Rescue Kit for this. Burn it to a CD, boot off it, and you can reset the administrator password.
I have no reason to believe Gooler's suggestion won't work but the one on Hiren's 10.4 will do that and will activate the account if desired even if it is deactivated.