Can't login to Mac

The Apple Mac computer is setup with rEFIt and boots into Windows XP.

I would like to boot into the Mac, however the username and password don't work.

I have tried rebooting and pressing Ctrl+S, but the command line interface didn't open?

http://www.wikihow.com/Reset-a-Mac-OS-X-Password-When-You-Can't-Log-In

Any help apart from a full installation.

I don't know if I can access the retail DVD.