Upgrading dual-boot Windows 7 to Windows 10

Hello!

A friend of mine has two disks a mechanical one and an SSD, both running Windows 7 and he chooses at startup which one he needs. Because the original mechanical disk was full we could not clone it on the SSD, so we kept the old installation in order to run certain applications he cannot find to reinstall and we clean installed Windows 7 on the SSD. Now he decided to upgrade one of them, probably the new on the SSD, to Windows 10. The question is, how the other installation will be affected? Will he be able to dual boot between Windows 10 on one disk and Windows 7 on the other? If this is lost I hope I can use bdcedit or EasyBCD to restore the Windows 7 boot entry. I am an experience user and I will probably be able to fix it, but I post here just in case anyone else has done it to tell me what to expect.

Thanks

PS: While at work I use a Windows 7 computer and I can browse all sites with latest supported Chrome, Firefox and Microsoft Edge versions, in my friend's computer there is a warning at ALL sites that the certificate is not valid or the date is wrong and he cannot use any browser except Pale Moon. Normally this issue fixes if you upgrade the browser, but they are all in the last version supported by Windows 7. Any ideas?

Check the system time and date on his computer.

They were correct. I even synchronized online, just to make sure. Nothing changed. I believe the computer is missing some important security updates, but if we are going to upgrade to Windows 10 there is no point installing them.

Because the original mechanical disk was full we could not clone it on the SSD

I would have used wincopy.

Now he decided to upgrade one of them, probably the new on the SSD, to Windows 10.

I suggest using the apply method and bcdboot. I have done it countless times.

Will he be able to dual boot between Windows 10 on one disk and Windows 7 on the other?

yes

spapakons said:

I believe the computer is missing some important security updates, but if we are going to upgrade to Windows 10 there is no point installing them.

The computer is missing KB4474419.

But you'll be unable to even run the Media Creation Tool without KB3140245 and EasyFix 51044.

https://support.microsoft.com/help/4474419

https://support.microsoft.com/help/3140245

Volume Z said:

The computer is missing KB4474419.

But you'll be unable to even run the Media Creation Tool without KB3140245 and EasyFix 51044.

https://support.microsoft.com/help/4474419

https://support.microsoft.com/help/3140245

I am going to upgrade from the ISO.