Reformatting the PC is an option. But if you have knowledge on the deep part of windows. Then continue reading.
1. Boot the computer into a Windows 7 installation disk (we won't do a complete reformat / reinstall / delete of the computer).
2. After its booting up. You will get a window with a button Install windows. Select "Repair your computer".
3. Select your operating system (obviously windows 7 unless you got a dual boot system)
4. Click Next
5. Select Command Prompt.
(At this point its kinda tricky)
5.1) at the console. Type in " C: " without quotes.
5.2) type "dir" no quotes
5.3) If you found "Windows" and "Program Files" You're at the right drive.
NOTE: If you didn't find these folder At C. Replace C with D (should be D: ).
Until you find those 2 folder. If not at D. go deeper. (I mean go from
C: to Z: until you find those 2 folder). A and B are reserved for floppy.
5.4) now type in "cd ?:\Windows\System32" without quotes.
NOTE: "?" corresponds to the letter on where you found the 2 folders
at step 5.3
5.5) type in "xcopy utilman.exe utilman.exe.true" without quotes (press F if asked)
5.6) type in "xcopy cmd.exe utilman.exe" without quotes (press Y if asked)
5.7) type "exit" without quotes.
5.8) select restart.
5.9) eject / disconnect Installation disk.
6. If computer has booted up. and its on the login screen. Select the Ease of Access button (Its a circle and
stripped. Can be found on the bottom left of the screen).
7. A console will appear (black screen with texts).
8. Type in "net user [USERNAME] <space> [NEW PASSWORD]" without quotes.
NOTE: In this case. it should be "net user Jon Jon mypassword". This changes
your password to "mypassword" but you could change it with your own.
and why Jon Jon you asked. Because you said the name of the account is
9. Close the window and try your new password. (A restart may be required in order for this to work).