Tech Question: Have i locked my keys in the computer?

[Sever]

Hey IWers. Been a while.

A techy question which may or may not be simple (started out simple enough).

A corrupt windows/system32/config/system file caused a boot error on the office computer. After doing a little searching for documentation, hunting around for the XP disc and trying to remember the old Dos skills, i was able to backup teh corrupt file and replace it with one from the XP disc using the recovery console. This only succeeded in extending the endless boot loop to the windows logo whereupon a new error message appears: "The value entered as the password does not match the variables of the password" (or something - it's only on screen for a second).

No problem, says i. I'll just go back to the repair console and put everything back where it was (and no one will be teh wiser ). Unfortunately, the password used to gain entry to the repair console has apparently been changed in that process, and i am now locked out of everything, in the rain, in a bad part of town.

Questions:

1. Is the password "value" or "variable" or whatever it wants to call itself stored in the sytem file that i replaced? If so, are there any likely default passwords that the system file would automatically set as the magic word in the event of the system file being replaced with the virgin file from teh XP disc? Administrator isn't it.

2. I've hunted around for other solutions: an automated system restore (no disk created, no go) and booting into safe mode (which is an option strangely lacking from the f8 boot menu...) Anyone know any other way? Anyone know why i can't boot into safe mode from the f8 menu?