It's quite a long procedure
firstly you need to back up theregistry so that the data is safe.
then click on start and press "regedit"
then click the plus near HKEY_Local_Machine
then + after software
then microsoft, windows, Current version, policies.
you will find a rating folder the click on to it
then on right side corner top select "key" then delete it
exit regedit and restart the computer
once restarted you will have to open IE >> internet option>> content>> click disable when asked for password either leave it blank or reset it
If you don't want to be get in to that technicalities http://www.stellarinfo.com/ is the link where you can find the windows password reset software I've used it to reset and recover passwords