Some time i get trouble with the *.AVi files that can not play on my AV500, here's how I fix it
1. Install Virtual Dub on your PC
2. Open *.avi file by Virtual Dub
3. On Video option : choose : Direct Stream Copy
4. On Audio option :
Choose : Source Audio and Direct Stream Copy
Choose : Interleaving
Choose Enable audio/video interleaving
On Audio block placement choose Preload 500ms and Interleave audio every 500ms ( This is important )
5. Press f7 and save the new file
Now the new avi file can play perfectly on you Archos
Have fun