For a system with a Dell OEM license the key on the COA should not be used. Instead the system locked preinstallation mechanism should be used which are applied at factory settings or with a Reinstallation DVD. Follow the instructions in my Download Windows 7 SP1 OEM and Retail .iso which instructs you in applying the Dell OEM SLP activation mechanism to a retail install using the ABR program and the Dell cert files I backed up from the Dell Windows 7 Reinstallation DVDs. Now is a good time to replace your hard drive with a SSD such as a 256 GB Crucial MX100 which will significantly increase the performance of your system. My A Clean Install of Windows 7 will take you through the entire install, including data backup, securely wiping, Windows 7 download, Windows 7 installation, Windows 7 Offline Update, installation of drivers and installation of Dell Backup and Recovery to make a new factory partition from the clean install.
I bought a dell laptop back in 2011 and after 11 months I HAD the hard disk drive replaced because it failed. Luckily it was still under warranty and installed windows on it without a problem and used the key (it was still clear back then) now in a week ago my laptop went into a bootloop and I reinstalled windows 7 on it using a usb but I coudnt read the key from under the laptop and I didnt get a CD when I bought it and as you read above there is no recovery partition but i still have the service tag dont know if that would help
WINDOWS 7 KEY RUBBED OFF