Some Windows users may find that programs such as Mercury, Mogul, Hermes etc fail to open correctly (the interface may start to appear but crashes immediately). If other programs such as ConQuest launch successfully then this is likely an issue with the graphics system on your computer.
The first suggestion is to ensure you are using the latest version (displayed on the CCDC home page).
If that does not help, the next step is to ensure that your graphics system's drivers are fully up-to-date. We would recommend downloading the latest drivers direct from the graphic system's manufacturers website. If you are unsure who this is, run the System Information tool (type "System Information" into the Windows search bar) and look under Components -> Display.
Links for Intel, AMD and NVidia drivers are below.
If you are using an external monitor, disconnecting it sometimes resolves the issue.
Lastly, if the above suggestions do not work, we recommend disabling 3D acceleration as discussed in this FAQ: Is there a way to disable 3D acceleration?