It is ubuntu, right? Regardless, I think it probably wants the (linux'*) root password.
If you don't know what it is, you can set it as follows:
(on the command line)
sudo su (it will then ask your user password)
passwd root (it will ask for a new root password)
And that's it.
* I think linux won't ever ask for windows's passwords, except when you're trying to access password-protected windows' shared folders.
Last edited by the dsc; 11-13-2011 at 04:41 PM.