So I don't use Windows but I saw Windows 10 on YouTube and loved it so I thought I'd get a tablet for it and avail the free upgrade. I found an HP ElitePad 900 on eBay advertised as new and bought it about a month ago. The tablet actually came with a scratch or two on the back side so I felt it was slightly used. It wasn't refurbished according to its serial so I think it was a display unit. Anyway I let it go and kept it. But yesterday I tried to set it up for Windows 10 update and the Windows 8 on it gave me constant activation errors. Here's the rundown of my situation: I found out that the tablet's hard disk was wiped clean, so no recovery partition. The Windows installed on it was Windows 8, but the sticker on it was for Windows 8 Pro. I used some software to find out the key embedded in BIOS, but this didn't activate the Windows properly. It said it was not activated in PC info, but claimed it was activated when I clicked for more info on that same page. The Windows 8.1 upgrade was refused on the Windows Store at first, but I sort of pushed it through by creating a new account and trying through that. Windows 8.1 Pro -- the correct Pro version -- downloaded this time but upgraded to an inactivated version. When I entered the key, it told me the key is blocked! With Windows 8, I got some weird partial activation (which I assumed was because the seller had installed a non-Pro Windows 8 and I was trying to enter a key for OEM Windows 8 Pro that was embedded in the BIOS) but it never said the key was blocked. I don't know if the key is actually blocked or I am just getting this message because I used some wrong pathway for Windows 8.1 upgrade. When I use Pidgen and enter the key I extracted from BIOS, it tells me I have a Valid Windows 8 Pro OEM key in BIOS. No mention of being blocked. I wasn't getting the Windows 10 update icon. As a last resort, I tried installing some KMS thing to activate but I still didn't get the Windows 10 update thing. Finally, some file I found through a YouTube tutorial worked and I have the Windows 10 update icon now and it's downloaded up to 4GB already in that hidden folder. So my question is: I will upgrade to Windows 10. Could the Windows 8 Pro OEM key embedded in my BIOS activate Windows 10 after upgrade? I feel I didn't follow the proper route to Windows 8.1 and so have neither a Windows 8.1 key nor a properly activated Windows 8.1 (that KMS thing is keeping this activated, not my BIOS key). Do I need to upgrade my BIOS embedded key to a Windows 8.1 key somehow and upgrade from a properly activated Windows 8.1? Or will Windows 10 read my BIOS Windows 8 Pro OEM key and activate?