Qgis cannot be opened after installation

Hi,
I just installed a new program on my laptop and when I tried to open the program this error appeared and it doesn’t let me to use the program. The installer is downloaded from a trusted website and is fully compatible with my Windows 7. Does anyone have any solution for this error ?
Thank you experts !

Qgis.exe – Entry Point Not Found
The procedure entry point
?load@QSystemLibrary@@SAPAUHINSTANCE_@@PBG_N@Z could not be located in the dynamic link library QtCore4.dll.
