Are you getting an error when starting the game? If I remember correctly, you need to install ".NET Framework 3.5" and some other updates, damn I can't remember which exactly.

To install the .NET Framework 3.5 go to the Cortana search and type "features" and selected "Turn Windows features on or off", then select the .NET Framework 3.5 from there. I can't remember if "Legact Components" "DirectPlay" is also needed.

Will not run is not very descriptive. I had it running fine on windows 10 just a few months back, then I ran a process of modding, that ran fine, NV also, fine on win10 and with mods. So it does work on win 10. What happens? Are you using galaxy? Have you installed to program files or outside windows folders? Are there any error messages?

Hi again, sorry earlier I said that the game requires NET framework. I meant that it requires a legacy DirectX version. I cant remember which at the moment, I'll post back later when I check my computer to find exactly which.

Edit, it's these two:
directx_feb2007_redist.exe
directx_Jun2010_redist.exe

Do you mean the 9c version that many games require?

https://www.microsoft.com/en-us/download/details.aspx?id=34429

But yes, we need more details. The poster doesn't give us anything to go on.

If any of the suggestions below don't help, check out the Fallout forum - https://www.gog.com/forum/fallout_series#1508378348 - spend a little time searching. If that doesn't help, try contacting GOG Support. If you and they working together can't get the game running (have patience, it'll take a few email exchanges I believe), you'll be entitled to a refund.

I too can't get the gog version of Fallout 3 to run on my Windows 10 system (the Steam version runs perfectly, even modded).

Frustrating. (same with Fallout New Vegas btw... no luck with the gog version but the Steam version runs perfectly).

Are those fresh downloads? I know they patched them shortly after release due to compatibility issues.

The downloads are dated June. I'll try downloading them again and see what happens. I don't think I've messed with them much since when I first downloaded them and couldn't get them to work.

Weird. I had no problem at all playing through the whole thing on my pure Windows 10 PC, which never even had a different OS version installed.

Fallout 3 can certainly run on Windows 10. I have done it myself.

However, if you have Intel graphics, that could prevent it from running unless you install a mod to make it compatible with Intel graphics.

If you don't have Intel graphics, then I'm not sure why it won't run for you, but the reason isn't just the Windows 10 OS.

Strange. For my W10 it runs perfectly

If your game crashes, if you have the goty edition, check if you have enabled all the dlcs, if not, that could be the problem.

Put that advice in a Delorean and send it to 2017.