What is it you are actually wanting to do ?
Mount one mac as a disk on the other to access it's files - File sharing
Control the mac from a far - Remote management aka screen sharing (you
use the mouse & keyboard to control the distant mac)
Send specific commands to make your mac do things for you - either
Remote login or Remote Apple events (both a bit geeky, you are likely
to know what they are if you need them)
Is your password blank? Just hit return when asked if that is the
case. Perhaps you have the username incorrectly formatted, check the
account name is the same as what you are entering.
It is possible to reset the password for any user account, it is an
option on the install disk. You boot from the install disk, and select
"Reset password" from the menu when it shows up a few screens into the
installer. The problem is that you will loose access to your keychain
items, so you really need to work out what the account password is if
you want to keep any keychain items.
Re:co