After a recent Steam update I started getting a warning about Windows Compatibility Mode. A quick check of both the shortcut and the executable itself revealed that no such setting was set. At first I was ignoring it as a fluke of Windows but it started screwing with my games… I need muh vida gumes!

The fix was simple, although annoying. Check the following regedit paths for the steam.exe executable. If you find any delete them and reboot.

• HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers
• HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers
• HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Compatibility Assistant\Persisted

This fixed the issue for me. Good luck to you.