First of all, what do you mean by "I lost the free upgrade offer to make the upgrade to Windows 10", msft still gives a free HWID for upgraders. You can establish a free HWID when you upgrade an activated Win 7 SP1 to 10 (Win 7 SP1 homebasic, homepremium > 10 Home or Win 7 SP1 pro, ultimate > 10 Pro). If your previous genuinely activated was by any key (oem systembuilder, retail, etcetc) it is lost (afaik) but if it's by slic table (brand laptops or pc's with pre-installed win 7) it shouldn't be a problem to re-upgrade to 10. You can also install win 7 sp1 and activate using daz loader and do the upgrade. Upgrading can be done by ISO (dvd/usb), MCT, Assistive Upgrade or Upgrade Assistent. You als can skip upgrading by going the gatherosstate route, you can find the howto, here: https://forums.mydigitallife.net/th...g-through-the-complete-upgrade-process.64770/
By "losing free upgrade offer" was that time range up to July 2016. I don't believe HWID is my case. This is a white box. The key was a perpetual key acquired via Dreamspark, Win 7 Pro. The upgrade itself is done. Win 10 is up and running no problem. The only problem is that I wanted that it to see the previous activation as valid...
Upgrading from an activated 7 will give a HWID aka Digital License for 10 on that hardware. When re-installing 10 just don't enter any keys and connect to the internet to let it connect to the HWID servers to activate. Please post the outcome of: slmgr /dlv
You can actually just activate it using your WIn7 key. I've done it with fresh installs on a dozen machines. It worked as of last week.
Install Windows Version of the legit Product Key and activate it as such, means for Windows 7 and 8.1 (could use P-Key of 8.0 and/or 8.1) start the Update to Windows 10 from within running Windows 7/8.1 and don't enter any P-Key if asked for one! After the install is done, have the computer connected to the Internet, restart and Windows 10 will be activated without question asked! Done, finish! I have done that the last time 2 days ago!
If I have Windows 7 activated by BIOS SLIC, upgrade it to W10, get free HWID, and then remove the SLIC from BIOS, will missing SLIC impact on my W10 activation?