You can often reset the administrator account password using a boot time recovery disk.
MS do one called MSDart, seems like you need technet to get to it though.
This one:
http://www.ultimatebootcd.com/index.html includes a utility called "Offline NT Password & Registry Editor" which sounds like it should do the trick
If those don't work I've prolly got one knocking around I could turn into an iso and chuck on drive or something.