Install ffdshow - Use MediaPlayerClassic for playing video. In MediaPlayerClassic >View >Options >External Filters >Add Filter >Select ffdshow Video decoder >Click on tick box >Select Prefer. Do the same for ffdshow audiodecoder. Select ffdshow Audio decoder> >Click on tick box >Select Prefer >Click Apply >OK. Play the video.avi file >Right click anywhere in the video window >Filters >Select ffdshow video decoder >Properties >Scroll down, select and click subtitles tick box >Apply >OK Close the MediaPlayerClassic and play the video.avi again. Your .idx and .sub files are automatically detected from now for any video file. Just see that all the three files (.avi .idx and .sub) must have same file name. Enjoy. AB
Or just use VLC Media Player, It supports most video formats and subtitle formats that are out there with out having install a bunch of codecs^_^
I forgot to mention, do this only if you don't like bulky VLC player (Installer itself is 20MB) and want to have a single exe file as your Media Player with all codecs built-in(MPC-HC.exe).