Windows 10: Acceptable activation serial key

I have/had installed on a number of computers, Windows 10 Enterprise x64 90 day evaluation edition. They are all expired by now, but still function for an hour or so I believe. I finally may be near buying serials keys for all the computers. The question is; Can I buy x64 Professional keys and successfully input them and activate the Professional version of Windows 10 even though Enterprise edition was/is initially/currently installed? Or, am I going to have to uninstall the Enterprise edition, and reinstall a Professional edition? I'm hoping to save all my settings and installed applications and not have to reinstall/configure everything all over again on every computer.

:)

 

Windows 10 serial on OEM


So I'll summarize steps made...

1. Saved serial number (taken with Belarc Advisory) from preinstalled (half chinese language) Windows 8.1 (don't know exactly the version, suspect Windows 8.1 with bing) on tablet
2. Formatted tablet
3. Tried to make a clean Windows 10 (HOME, HOME N and also PRO, everytime with the same result) install with ISO taken with MediaCreationTool, during install (and also after completing installation) it says that the saved serial is not valid
4. Tried to reinstall Windows 8.1 (ISO taken with MediaCreationTool again) HOME, it says that the serial is not valid

So i suspect that the saved serial, is from a WINDOWS 8.1 WITH BING OEM version and this kind of ISO is not accessible/downloadable anywhere (at least I can't find it, any suggestion?)

Still not tried SHOWKEY with that serial, I am in office now, and the serial is saved on a usb pen at home, will try this evening.

So I'm stucked but if everything is like I suspect, it's incredible. If I have a tablet/notebook/netbook with Windows 8 preinstalled, it seems that I can update to Windows 10 without problems, but if I want to make a clean Windows 10 install that serial is not valid...

 

I need to activate Windows 8.1 which I updated to Windows 10 as suggested, but still the program is not accepting the key.

Original title: activate program

I need to activate Windows 8.1 which I updated to Windows 10 as suggested, program is not accepting serial number on packet or any other password which I tried to reset

 

Wndows 10 does not accept product key

I got that Hans, but if this steps are taken:

• create the install media
• boot from install media
• format the drive
• begin the install
• skip the key (since it does not accept the w8.1 key)
• finish install

Then what happens? Am I just SOL? Do I have to pay for Windows AGAIN? There has got to be a way to call MS and "convert" a key, or get a replacement one...