Did you receive a specific request for a password...or are you just assuming that's the problem?
I guess that I'm curious how you connected the drive...when you discovered all this...if the system won't boot wth the drive connected?
One possible factor to be considered: Did you change the jumper setting when you tried to boot from connecting to the PC?
That Access Is Denied message frequently happens when moving a boot drive from one system to another...what has to happen (in some cases) is the user must take ownership of the files/folders which belonged to the former system/owner (My Docs, Docs & Settings, etc.): How to take ownership of a file or folder in Windows XP - http://support.microsoft.com/?kbid=308421
None of this may apply in your case.