you'll need to connect to the mmc you just created as an admin.. if you use the same login/pass for both pcs, you shouldnt have to do anything. if it's the same login/different pass, change the pass on your pc to the one in the attic.. if they're completey different login/pass, just create an admin account that mimics the login/pass from the attic pc.
if it's a completely different login/pass, save the mmc console somewhere like the desktop.. right-click and do a "Run-as" and login as the admin account you just created..
i tried using the admin account on my other pc, PCNAME\Username but i get an error.. been a while since i messed around with win2k... ah well. it's friday.. dont want to figure anything out..
