Forgot Your Account Password
For Lion/Mountain Lion
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
When the menubar appears select Terminal from the Utilities menu.
Enter resetpassword at the prompt and press RETURN. Follow
instructions in the dialog window that will appear.
Or see Reset a Mac OS X 10.7 Lion Password and
Your username is the foldername under your account folder located in the /Users/ folder at the top level of the hard drive.
Thanks to all for your suggestions. It was a very interesting foray into the hidden world of terminal commands and single user scripts (none of it worked btw). I have achieved success by going back to the very beginning of the problem solving process. Initially I couldn't get a restore working to wipe the problem. I was getting a message that my iMac didn't have enough memory to restore the HD. This didn't make sense, and because my 6 year old Mac had never given me any problems, I had to go through a learning curve and had to discover in an aha moment 3 days later that there was a pull down menu in Time Machine that zeroed in on just the contents of the HD that should be restored. What I had done as a newbee in backing up with TimeMachine was leave my 2 external drives open on the desktop when doing my first backup. So what I've been saving in one backup file is the contents of 3 drives. I didn't know that you couldn't later select a specific drive within the one restore file. Thankfully I had a 4 month old backup of the iMac HD and haven't lost too much important data. What a way to learn to use Time Machine correctly. Thanks again for the support...gotta run and do some backups seperately for each device.