How to fix Class not registered or 80040154 error
"Class not registered" is one of the most annoying and frustrating error message I ever got because none of the video files can be played by Windows Media Player, Media Player Classic or other DirectShow player and common fix methods (Windows Media Player reinstallation/upgrade, codec reinstallation...) seems to fail.
Fortunately, the solution (in fact one of them because there are few different solutions) for this problem is very simple.
After some research I found that quartz.dll (a DirectX related DLL) wasn't registered correctly.
How to register it?
Click on Start > Run... > and type regsvr32 quartz.dll
In the end, you should receive a message saying that your file was succesfully installed.
Note: Please, let us know if the solution suggested here wasn't helpful for you so we can try to complete this guide with other hints.
"The module "quartz.dll" was loaded but the call to DllRegisterServer failed with error code 0x80070005.
For more information about this problem, search online using the error code as a search term."