I have built "around" an old PC using a mix of new and salvaged parts, and thought I'd install Windows 10 "clean". I built on a workbench and didn't connect to the Internet while doing the initial Windows install, and now it's asking for a product key.
My product key dates back to Windows 7 and is too long / has "unacceptable" characters for the key entry function. I've signed into my Microsoft account in apps including PC Health Check without issue, but can't seem to get Win10 to recognize this.
I can always start over and reinstall -- I'm only a couple hours into this -- but I maybe I'm missing a stupid obvious thing.