password not working!

after iMovie refused to come on
I tried to re install from the restore disks.
All I wanted to do was reinstall iMovie,
so I thought I shut off all other installations.
Guess I was wrong .......
After the restart of the restore/installation
the window that came up asked for my password.
It didn't work.
After a few attempts
the hint came up
and it still didn't work.
Now I'm locked out of my computer .....
Now what?
(I'm using my old bronze to get online)