Posted 20 December 2017 - 09:51 PM
If you upgraded the same hardware you have now you can reinstall with the newest Windows 10 ISO and NOT use a key 99% of the time (just be sure to select the proper version) and it will activate when online giving a message of "Windows is activated with a digital license"
If you used the Windows 7 key on the same hardware that should still be an option again now, it may also work with dissimilar hardware assuming it was a retail Windows 7 key
If you use a Microsoft account that adds another layer of activation records that should allow you to activate the same hardware again.
Overall it's pretty straight forward and if you don't mind some extra hassle you can actually still do a free upgrade today, or at least it still worked last week for me. It requires the original Windows 10 ISO upgrading over a legit windows 7/8/8.1 install with the internet disabled until the windows 10 upgrade is complete.
i7-5930K/GA-X99-UD4/32GB G.Skill/512GB Intel 600p/512GB Crucial M550/480GB ADATA SP550/5TB/GTX 1080 Ti/Rosewill Capstone 1000-M/Rosewill Blackhawk (main rig)
i7-4930K/GA-X79-UP4/32GB G.Skill & Team Vulcan Mixed/240GB Seagate 600 SSD/4 x 1TB/GeForce 315/Rosewill Capstone 750/Corsair Carbide 200R (VM Server)
i7-6820HK/Aorus X7 v6/16GB G.Skill/512GB Samsung SM951/1TB/GTX 1070/230w AC Adapter/94.24Wh Battery (Gaming/Fun Laptop)
i7-7500U/Razer Blade Stealth/16GB/512GB Samsung SM951/45w USB-C AC Adapter/53.6Wh Battery (Work Laptop)
i7-4770K/GA-Z87X-UD5H/16GB Kingston/240GB Seagate 600 SSD/2TB/GTX 1070/Rosewill Capstone 750-M/Rosewill Blackhawk (the wife took this one)
i5-3570K/GA-Z77X-UD5H/24GB ADATA/120GB Crucial M500 SSD/2 x 8TB/3 x 5TB/4TB/2TB/Antec BP550/Bookshelf (server)
i5-8600K/ASRock Z370 Gaming-ITX/ac/16GB Team Dark/512GB Sandisk 400 SSD/GTX 1070 Ti/EVGA Supernova 650 G1/Phanteks Evolv ITX (HTPC)