Use a tool called MediaInfo to examine the file. See if there is a separate entry for a subtitle stream in the avi file. (I doubt there is, as most avi files don't have them)
Opt out of the AOL tool bar by the way. Not too happy about the extra "option" in this installer, but it is otherwise harmless.
I find the Tree view within MediaInfo to be the most informative. You should be able to right click on the video file and see an option there to open the file with MediaInfo.
If your avi file has the subtitles showing up below the level of the video itself, then you can crop that out with AviDemux or Virtualdub, then resize to fit whatever resolution you need. Many avi files will have hard subs superimposed on top of the video however.