Crash on startup, with a new install

Are you shutting down all non-essential programs (especially anti-virus) before starting the game? Firewalls can cause conflicts (generally on startup or loading screens) and overlays from graphics tweaking/monitoring programs or chat programs can also caused issues.

If you have any generic or obscure USB controllers (or other devices) plugged in, try disconnecting them. Crashes on startup with faulting module names of ntdll.dll and EZFRD64.DLL, can (particularly for the latter) be related to USB controllers or PS2 to USB adapters (for various games).

Can you start the Classic version of the game?
Try exiting out of the Steam client, and starting the game directly from the '..\SteamApps\common\Divinity Original Sin 2\DefEd\bin\EoCApp.exe' program file, by right clicking and running as administrator (or '..\Divinity Original Sin 2\Classic\EoCApp.exe' for the original release).
Try right clicking the executable, select Properties, switch to the Compatibility tab and check off the 'Override high DPI scaling behavior' option (set it to Application), maybe run as administrator and disable fullscreen optimization, and set a Win 7 or 8 compatibility mode.

Try verifying local files: in the Steam library, right click on the game and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Files...' button.
With the GOG version, in the (optional) Galaxy client, select the game, then the settings icon at the top right (beside the Play button) and under Manage Installation select 'Verify / Repair'.

Especially if you have a relatively high desktop resolution, you can try temporarily lowering it, to limit what the game will auto-detect. If that allows the game to start, you can then exit and restore your desktop resolution.

If you check the Event Viewer, does that give an error code or 'Faulting Module' file name that might help identify the cause of the crash?
- click Start (or WinKey-R), then type "event viewer" into the search box. in Windows 10, 'event' should bring up 'View event logs'.
- after starting the Event Viewer, expand 'Windows Logs' in the left column and select 'Application'
- in the center column, look for a recent error for the game (maybe sort by Date and Time, or search for 'EoCApp')
- check the information under the 'General' tab below the list of events, starting with "Faulting application name..."

Check for updated graphics drivers, and Windows updates in general.
For Windows 7, please make sure you have Service Pack 1 installed. That is the minimum required version of Windows (64 bit).

Normally, Steam will install the redistributable packages if required when you first start the game, or GOG during the install, but you can check, and reinstall them manually:

- Visual C++ Redist 2017 (64bit), now included with the 2019 release (if this is a problem, generally there should be an error when starting from the executable, mentioning a VC related dll). In the Control Panel, Programs and Features, try right clicking the MS VC++ 2015-2019 redistributable entries (32 bit and 64), if listed, and select Uninstall and then Repair. Otherwise:
C:\Program Files (x86)\Steam\SteamApps\common\Steamworks Shared\_CommonRedist\
C:\Program Files (x86)\GalaxyClient\Dependencies\__redist
or https://support.microsoft.com/en-ca/help/2977003/the-latest-supported-visual-c-downloads

- .Net Framework 4 (if the launcher starts, this should be fine)
https://www.microsoft.com/net/download/dotnet-framework-runtime

If you get an error mentioning the api-ms-win-crt-runtime-l1-1-0.dll file, or similar, it is part of the Microsoft Universal C Runtime, and on Windows 7 or 8.1 can be downloaded here, or gotten through Windows update (it is already part of Windows 10).

Try browsing to the '..\Documents\Larian Studios' folder and delete the 'Divinity Original Sin 2 Definitive Edition' folder.
This folder contains the saved games, configuration files and a level cache folder. Normally it would be better to rename the folder for troubleshooting purposes, but if you don't have any saved games that isn't an issue.
Next, extract the replacement folder from this download into your '..\Documents\Larian Studios' folder, and see if that will let you start the game.

The graphicSettings.lsx file is set to 1280x720 Windowed mode, Very Low quality preset and low audio quality, which you can change in the options (manually, or hit autodetect) if this gets the game to start.

Try doing a clean boot and then test the game. Click Start, or hit WinKey-R, type in msconfig and hit enter; in the General tab, click Selective Startup, uncheck Load startup items (if required) and leave Load system services and Use original boot configuration options checked. Next, click on the Services tab, check the box to Hide all Microsoft services, then click the Disable All button (maybe make a note of which are currently enabled/disabled), then click OK and reboot the computer.
Run msconfig again to switch back to the normal boot configuration.

If that doesn't help, please contact support with a dxdiag report (WinKey-R, type in dxdiag and hit enter, then when it finishes loading click on the 'Save All Information...' button and save the report somewhere handy). Also check the '..\Divinity Original Sin 2\DefEd\bin' folder for the gold.log file, and if there are any 'CrashDump' files being created, zip a few together to include.