Okay well, if you want to satisfy your curiosity and know where the registered files are you can search the registry (regedit).Mainly curiosity to be honest...
Good idea, thanks. Interesting. Found that psisdecd.dll is correctly referenced to my dvbfix folder. psisrndr.ax is mentioned but I saw no file path. Couldn't find mpeg2data.ax anywhere even though it was successfully registered using regsvr32...