I can recommend this site for Windows keys, recently bought a window 7 pro licence to add to my dual boot windows 10 desktop. Simple as you like, paid for, key sent by email and installed in just over 5 mins!
The site is the off shoot of a site run by Softwaregeeks who ran there key sale site a few years ago, prices are great, Windows 7/10/ plus Microsoft office and other software is on the site, There after sales support is very good also Give them a try!
Genuine License Keys for Windows and MS Office – TheUnitySoft
