REGSVR32 /u SHMEDIA.DLL
here regserver is the program for managing dll (dynamic link library) files , that you can say act like plugins for windows for extra information or managing some particular process .
If you had installed some program which showed info for the media files , it had registered with the media dll to show info for the files . but due to some reasons (got corrupted) it was unable to show info and your system hanged .
/u stands for unregister , thats what shmedia.dll got unregistered and came to the default by windows , you can say your media info plugin got unistalled (or dll got resetted)
And you are happy now
