Vista Password Problem

I have a Dell desktop with Vista home premium. I setup a password and it has
worked very well until today.
When I start the system up it completes the boot routine and then come to
the password screen. I know the password and when I go to enter it nothing
appears in the password field. I can type all I want but no characters show
in the password field. When I hit enter/go it says "password incorrect"

Thoughts on how I fix this problem.


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