How to watch idx and sub file properly?

I got a load of films which come with .srt sub which display perfectly fine but more recently I have noticed a lot of films coming with .idx and .sub files instead and for some reason I cannot get them to display correctly... What am I doing wrong, is there a easy way to convert them to .srt?

Sorry wrong section was meant to post in general computer topics

Moved as requested

just found this dont know if it will help m8



1. Download "Media Player Classic".

http://www.filehippo.com/download/file/1…

2. If it was a video file, go to (File==>Open File) and choose the video file you want to watch, or if it was a DVD, go to (File==>Open DVD).

3. Go to (File==>Load Subtitle) and choose either the ".idx" or the ".sub" file, the subtitle should appear.

I can get the subs to be displayed but they are small and distorted unlike the .srt files.