Before we start, please remember these things. It may take more than one step/answer to solve a problem. So If my answers didn’t worked or if you are not satisfied, please don’t Rate my answer bad/negatively (First two left Stars/Faces/Ratings are Negatives) but please Reply back to me by clicking the “Continue Conversation” or “Reply” button. Remember, only Rate answer after you are 100% Satisfied.
If you don't have the discs, then you can create a new user account from Single User Mode. Then login to that new account and you can change the password XXXXX your old account. Follow the steps below to create a new User Account in Single User Mode.
mount -uw / rm /var/db/.AppleSetupDone shutdown -h now After rebooting, you should be able to create a brand new Administrator account. Then goto System Preferences > Accounts, select your old account and reset the password XXXXX there. Then logout from Apple menu and login to the old account.
Let me know if that didn't worked, so we continue troubleshooting. Don't Rate my answer until you are satisfied.
Then login to your new account, goto go back to XXXXX and click Security. In Security, click General ab. In General, enable "Disable Automatic Login" option. Close it. Restart your Mac. Then login to old account. Then just delete the new account from System Preferences > Accounts
If that didn't worked, then goto Macintosh HD > Users > your user name > Library > Preferences folder and trash the com.apple.keychain.plist file. Trash anything related to Keychain from there. Then restart your Mac. Does that worked ?