no one will help you 'free download' windows key. don't ask for it.
you gotta buy serial numbers from microsoft or any authorized reseller.
if you have a serial number related problem, ask dell support or microsoft customer support.
piracy is not allowed on tomshardware.
check the your laptop box/paperworks/manual. you should find your windows' serial (if your laptop came with windows preinstalled and with an windows installation disk.) in there.