DW runs just fine in Win 10.
Which version of DW is giving you troubles? There was the original version on CD, the Steam version, and the direct download/install version from Strategy First.
Off the top of my head, I think you're talking about the d3d8.dll install. You can find the DLL here, just make sure you install it in the SAME folder where the dangerouswaters.exe file resides.
As an example, if you want to run the current version of the RA mod it already has the d3d8 file included in the download, HOWEVER the .dll is found in a separate folder. Just move the dll from its folder out to the main DW folder. Rule of thumb, if you see the actual DLL file and the DW .exe file in the same folder- you're OK and you've installed it right.
There's also a way to run the game in Win 10 in windowed mode, but I don't use it. Chazly and some of the other folks can answer how to set that up.
After that, you'll need to make changes for things like display size and type by manually editing a file called dangerouswaters.ini in the game's main folder. Just double click the .ini file and Win will ask what program you want to use. Be sure to select Notepad. You can find info about what to edit in the INI in other threads on this (DW) forum.