John, you are in luck as Ubuntu makes password recovery a snap. And by the way, thanks for taking advantage of my premium help option — it’s awesome folks like you, that make this website possible! You asked this question yesterday and as promised, I am providing a solution in less than a day. Okay, back to your quandary…
The key here is being willing to write down the information on this page, so you can take it with you to the affected computer. I suggest writing it down, as you will need to follow these steps carefully, as to get things back up and running asap.