The Witcher 3 not installing!

It would help if you specified what error message it gives you, alongside a few screenshots.
P.S: Welcome to the forums, your topic is fine.

It is the same error if you try to install through gog installer or galaxy gog?

Try coping all the data from the disc to Hard drive and see it is able to do that. This will ensure that DVD is working. If yes, try to run the install from the copied data and see if it installs. Check for any prompt at the bottom of the screen as well, if a security software or windows 10 is asking for permission to execute an application.

If you have good intenet, you could try to activate the key on GOG.com and download the game from there. If your disc is faulty, then the download should help. Hopefully you don't have limited internet though :/

You can also try asking around on their support forums, here's the link: https://www.gog.com/forum/the_witcher_3_wild_hunt#1446385947

EDIT: Also, in case it's an issue that someone has had already, I've used the search button on their forums just for you. Have a look at these topics: https://www.gog.com/forum/the_witcher_3_wild_hunt?search=installation%20error

As nopzor said, the error code would help greatly.

Hmmmm, doesn't retail Witcher 3 come with a GOG key? If it does, make an account on gog.com, and enter the key here - then you should be able to download the whole thing. Hope you have some fast internet, good luck... :)

It doesn't matter if you had a level 3 Witcher, you need an Installer to install, not a Witcher.
A blacklist is enough, no need to report me.

A more serious approach: maybe the problem is in the unpacking process of the compressed files, try doing it manually