Enter is the only default password I know of, however I expect you have tried that.
The ways to reset the XP Admin password are long a fiddly, also not everything is recovered, for example if you have used the NTFS file security settings I believe that they are much harder to recover, but I don’t know as I have never used them.
http://home.eunet.no/~pnordahl/ntpasswd/bootdisk.html has some useful things that might be worth looking at.
Is this a new install? If so it might be quicker and easier just to install from scratch again, if not – good luck!