Do you have your OSX disks for this machine?
In that case the easyiest thing to do would be to just go ahead and reset yoru Admin password XXXXX the OSX disks.
To do this can you follow the steps for resetting your Admin Password XXXXX this Apple article http://support.apple.com/kb/HT1274
If you run into any problems or need any clarification just let me know
More than welcome,
In future make sure to tell any tech that works on your Mac that you wish whatever you have to be used as your password XXXXX that they will always set it to something you know and so it wont mess up your Admin rights or keychain.