I've got ArcGIS Desktop 10.5.1 installed on a PC running 64-bit Windows 7. When I go to open ArcMap - whether from the exe file, an exe shortcut, or an existing project file - the splash screen appears for some seconds, but then the program doesn't open. I can open some other ArcGIS components (e.g., ArcCatalog, ArcReader) no problem, but others (e.g., ArcScene, ArcGlobe... the "viewer" applications?) act the same as ArcMap: splash, then nothing. I tried deleting the normal.mxt file, to no avail. Any ideas on what's going on and how to fix it will be much appreciated.