The following are three tools to use to examine your hard drive and search for Microsoft Windows and Office product keys that will make re-installation simpler and cheaper:
They each have their pluses and minuses. I like Enchanted Keyfinder the best because it is open source, however until this tool is improved, the other tools do a better job of recovering product keys. Antivirus software falsely claims the other tools are malware, but Enchanted Keyfinderdoesn’t even raise a blip. The other tools try and push you to purchase upgraded products; the basic version is all that I am advocating. Magical Jelly Bean Keyfinder tries to install extra unneeded software, so pay attention to the options and opt-out of anything but the Magical Jelly Bean part. I hope with ongoing development, Enchanted Keyfinder can make the other tools obsolete.
All these tools return only what is available on the disk. Many OEM installations of windows does not have a real license key written to the disk. The disks are mass copied to keep costs down. But if you have installed from disk in the past, these tools can help recall your legitimate keys for a reinstallation.