Question on Subtitles

[SeptimusFry]

I have acquired an old film which is supposed to be complete. It is in French. I have a AVI file and an IDX file. From searching here, it seems that I should have a SUB file in order to see the subtitiles. Is this correct, or is this something clever where the SUB is integrated in the AVI and the IDX points to it.
There is no file reference in the IDX file. The following is a possibly significant part of the IDX file...

>>>>>>my arrows
# Language index in use
langidx: 0

# English
id: en, index: 0
# Decomment next line to activate alternative name in DirectVobSub / Windows Media Player 6.x
# alt: English
# Vob/Cell ID: 1, 1 (PTS: 0)
timestamp: 00:00:37:937, filepos: 000000000
then lots more timestamp, filepos pairs right to end of file
>>>>>>>>my arrows

I hope someone will recognise what is required here as, although I live in France, my French is not so hot.

[Hoser Rob]

"Acquired"? (insert smirk/wink emoticon here)

Try a subtitle site. IME opensubtitles.org is the best. Subscene is good too.