Forgot admin password on MacBook Snow Leopard, Install disc is stuck

Can someone please help - I reset my password to my computer (have no idea why), and I must have hit a wrong key in doing so.

Now, I cannot log in - I installed the Original disc from Apple, and now it is stuck in the laptop.

When I open the computer, the screen I see is the log in box, with my name, but I do not know what key I

mis-typed in the password. Have tried all variations, no luck.

Thank you, SO much, in advance for help.