Forgot name/password and install disc does not allow me to reset it

Question

I forgot the Name and Password I set up to log into my imac. It is an older imac, from 2006 and I can't remember which version operating system. I have tried to use the install disc to reset the password, but it does not allow me to do so. Is there a way to reset the name and password without the install disc? For as long as I can remember whenever I would turn on my mac there would be an image that I had chosen and then a field to enter password. Just recently I turned on my mac and the image or avatar was no longer coming up and it asked for Name and Password. I have tried every combination I can think of and nothing works. I have tried to reset using my install disc, but it says that I do not have a password to reset. 

Answer 1

Before giving up try the following technique to determine the user account names, and reset their passwords if necessary.
1. Shut down your Mac and turn it back on while holding down the ⌘ and S keys at the same time until your see a black screen with white text. This is known as Single User mode.
2. You can skip the following step, but it is recommended that you do not because it will check your boot volume for errors and correct what it can:
At the :/ root# prompt, type fsck -fy and press Return or Enter. It will take a few moments to complete. If you are concerned that nothing is happening just press the Return key until you see the :/ root# prompt again. Once the file system check is complete and the prompt returns, type mount -uw / and press Return / Enter.
3. Type the following
launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist
and press Enter. If you get an error message you may ignore it.
4. Type ls /Users and press Enter. All of the usernames on the computer will be listed, which is helpful if you don’t know or remember what these are. You can skip the next step if you found the user name you recall and know its password.
5. Type dscl . passwd /Users/username password while replacing username with one of the users displayed in the previous step and replacing Password with the new password of your choice. Press Enter. You may get an error message about a file or directory not being found. You may ignore this.
6. Type reboot and press Enter.