I have installed Morrowind GotY to C/Gog Games/Morrowind and am now trying to install the mod Morrowind Overhaul 3.0. Part way through the mod install it asks me to select the ‘Morrowind.exe’ folder but it won’t accept C/Gog Games/Morrowind because the mod has changed the file name ‘Morrowind.exe’ into ‘Morrowind.Original.exe’.
Please, where do I find the file containing ‘Morrowind.exe’? I have tried searching C: but it only comes up with the Gog Games /Morrowind folder.

Have you tried making a coping of morrowind.original.exe and renaming it back to morrowind.exe? It’s been a long time since I used overhaul.
TBH you may be better off using OpenMW which has come a long way.
Also, you will want rebirth:
https://www.moddb.com/mods/morrowind-rebirth
Which can be compatible with overhaul with some tweaks (there is guidance in the documents or search for install both).

I remember that overhaul 3.0 worked really nice with gog version of Morrowind, but same here, long time since then.

And not only that, Overhaul 3.0 isn't recommended anymore as I know and it is considered outdated.

Rather check Rebirth as said above, not only that, there is also nice recommendations by trancemaster itself about mods which are compatible with Rebirth, must check that, if you want.

https://www.moddb.com/mods/morrowind-rebirth/tutorials

Many thanks for your replies. I have, as suggested, removed the 'Original' from the exe file and the mod has installed correctly. I do in fact have five different collections of Morrowind Mods (and could produce more!) and am trying them one at a time. - being retired gives me the time to. I have tried the selection lifted from the GoG forum and it works well. The Overhaul 3.0 mod I find to be slow and rather dark on my PC so I will try the selection from 'Morrowind Modding, then 'Morrowind 2021 mods' and then 'Morrowind Best mods'. Hope to play the game one day!!
Again, my thanks.