how do I bypass a password window?

I had an issue with a Kaspersky product on my dell 620 / windows 7 computer. Kaspersky Technical Support suggested  I reinstall the product. I uninstalled the anti - virus and then clicked restart as prompted.....as soon as it got to the window that asks for my password - before going on to the startup page - my mouse and keyboard froze dead...devices only work the first few moments during startup. How can I bypass the password page so I can fix the problem and get the mouse and keyboard working again.....I'd love to do a total restore on the darn thing..... but I bought it at sam's club and the computer did not come with any windows 7 disks - which tells me it has to be a referbished model. I tried to use the drivers disks, but no go. Hopefully someone here can help...... both Kaspersky and mt internet providers were a bust.