I hope Vikram above is right in that you did not delete the wrong Reg Keys.
Are you logging into a domain or the local machine when this happens- getting logged out right away?
Either way, connect to the machine remotely.
rename any user profiles currently stored on the machine. Add something like old_ before the name or something. Anything to force the system to create a new acount and locally stored credentials.
Than try logging into the machine.
Works? There are some residual data in the user profile that needs to be removed or cleaned.
Does not work? You will need to repair your Windows installation in order to recreate the proper registry keys and values (if applicable).