You need a program which can read the subs, f.ex. VobSub. You can get that here:
http://www.afterdawn.com/software/video ... vobsub.cfm
After installing that, you can use wmp, powerdvd, vlc or whatever to play your movie.
To make the subs work properly, the name of the .avi file has to be exactly the same as the subtitle file. The two files also has to be located in the same folder. When the subtitle is running, a green "arrow" will appear in your system tray.
I hope this helped, good luck