after reboot an error message displays "you are not authorized user windows will close"

windows does not close and the error message is frozen on the screen.

faq at vendors web site address problem with instructions to run regdelete and navigate to a specified line of text to delete auto log on of default user.

my problem is windows does not stay open long enough for me to use the run command.

so, how do i get to a C prompt or to the run command or get windows to close.

how do i get to regedit from this self created delima?