Yes that was what I meant. It worked on my machine but as I only have one avi file with the IV50 codec (and i'm not 100% sure that it is IV50 (it says so in VLC but...) so I don't have that much to go on.
The only other option I can think of is using Mplayer (download the complete package from here:
http://mulder.dummwiedeutsch.de/home/?page=projects#mplayer )
Atleast on Mplayers website it says it has support for Indeo 3, 4.1 and 5.0 - but the question is does these codecs work on Windows 7 x64 ? - because if they don't you're pretty much out of luck I can't see Ligos (the current owner of the IV50 codec) spending much money to make a codec for Windows 7 - I don't think there's much money in it.
If Mplayer doesn't work you might wanna install XP-mode (and Virtual PC) on your windows 7 machine (download link here:
http://www.microsoft.com/windows/virtual-pc/download.aspx ) - and then installing the codec in the virtual pc. Or you could install VMware Workstation and run Windows XP on top of that (and installing the codec). Both of these ways are almost 100% certain to work but it is a lot of work for some outdated video-files.
Hope some of it helps.
Regards
RabidSquirrel