Subtitles: idx and sub files

[uly]

A total noob question: I have a subtitle that came with 2 files, one with extension .sub and one with .idx. What do I do with them? I've found somewhere that these .idx subtitles are for use with VobSub, so I installed the DirectVobSub filter from the Nimo pack, but it doesn't seem to do anything. What should I do?

[gd_nimrod]

Keep those files in the same folder as your video file, then you can play the video and the subtitles will appear. Even WMP9 supports this.

[uly]

I'm not sure if this is the problem but I'm still using WMPlayer 6. Subtitle does appear work with .sub and .srt and some other file formats, but not this one, which, as I've mentioned, come with both a .sub and a .idx file. I don't know, but I doubt, that this is the files' problem. I think I have DirectVobSub installed but I don't know how to use it.

[Rzecz]

I've also had problems with some sub files. Could they be formatted wrong?
I have one sub file that works with VobSub, and another sub for the same movie that doesn't work.

The working file has this format:
00:00:30,287 --> 00:00:33,017

While the non-working file has this:
00:00:30.28,00:00:33.01

Is the time format the problem with the second file? Or is it because it has a header with title, author and such that VobSub won't read?