Answer

Thank you for the quick reply.

Try to login to the default administrative account through safe-mode:
1) Start your problem vista computer and "as soon" as it begins to turn on start tapping the F8 key on your keyboard till you are prompt with an advanced option menu that has options like safe-mode and safe-mode with networking. Then scroll to safe-mode with the arrow keys on your keyboard and push enter then your drivers will load and it will bring you to a login page. You should see an account there that says Administrator. Please click on that and if it asks for a password don't type anything just click ok/login and once logged into the admin account then click the globe at the bottom left to bring up the start menu then click on control panel, then on the left side click on classic view if you aren't already in classic view, then on the right side click on "user accounts" then click on your account and then click on change password make the password what you want it to be save it and then restart your computer and see if you cacn login.