MPEG-4 to AVI help

[cosmo09]

Hello there
I have tried to convert a MPEG-4 file to AVI using RiverPast Video Cleaner Pro. The software looks really easy and intuitive to use, but the converted AVI file was sized no less than 19GB (!).
Now, I have read on RiverPast website that this depends on the codec used (I used Microsoft Video 1, which Video Cleaner Pro gives by default). So my question is, which codec should I use, where could I get it and where should I install it? Also, will it be compatible with my standalone DVD/DivX player?
Or, alternatively, should I just change resolution and frame-rate (and, in that case, which res and fr-r would be appropriate)?
Or, second alternative, should I use a different software that gives the possibility of a target size for the converted file ? (Video Cleaner Pro doesn't offer that option).
This is a lot of questions, I just realized... Well, thank you all in advance for your help

[Baldrick]

mpeg-4 file? a .mp4 file? or what kind of file are you converting?

[cosmo09]

Yes, .mp4
thanks

[45tripp]

Probably got a AVC AAC combo.
Use Avidemux to convert to Xvid video with mp3 audio.

[cosmo09]

Help, anyone else...? Please...