Having Steam and/or the game installed on a different drive should not be a problem.
Did the crashes with D:OS and Way of The Samurai 4 start at the same time? Or did you only install the other game after you started having a problem with D:OS?
Try browsing to the '..\Documents\Larian Studios' folder and renaming the 'Divinity Original Sin' subfolder.
This folder contains the saved games, configuration files and a level cache folder. Deleting or renaming it will get the game to recreate it on startup; playing the game from a different Windows user account would effectively do the same thing.
If applicable, first disable cloud support, either globally (in the client click on the Steam menu and select Settings, and then Cloud) or just for this game (in the library right click Divinity: Original Sin and select Properties, then switch to the Updates tab and check the Steam Cloud section).
Next, see if you can start D:OS. If so, create a new profile (with cloud support enabled, Steam would just sync to the online version of the profile), and maybe double check that you can start a new game and save/load. If that is fine, exit and then copy a couple saves from the renamed folder into the newly created profile's savegames folder. If that lets you load the saves, move the rest of the saves over.
If that doesn't work either, delete the new My Documents D:OS folder and rename the original back again.
Try deleting (or moving/renaming) the d3dcompiler_43.dll file in both the 'C:\Windows\system32' and 'C:\Windows\SysWOW64' folders, then reinstall DirectX 9c and reboot. If that doesn't help, try copying the dll file into your '..\steamapps\common\Divinity - Original Sin\Shipping' folder.
Try checking your system files:
- click Start, type cmd into the search box, right click the program and run as administrator
- type the following command and hit Enter
sfc /scannow
- when that is done, type exit and hit Enter, then reboot your computer.
Try a clean reinstall of the most recent video drivers (
guide). Try checking for Windows and driver updates in general.
