Rar files (from http://www.netknowledgebase.com/tuto...net_intro.html):
Rar files: Another compression/archive format. This is most commonly used on iso or bin files in order to split them up into smaller files (15 MB is the norm). Winrar and many other utilities can decompress these. Rar files are usually in the format .rar, .r01, .r02, etc. But don't be surprised if you don't see a .rar file. Just open up winrar and point it to .r01. You also may see them packed as .001, .002, etc. (maybe with a .rar, maybe not).

Do you have some sort of rar program on your computer that is stealing possesion of the files? Or trying to compress the files as soon as they get into the system? Worst case it sounds like you could just decompress them.

The other thing could be, are you using a download accelerator program? I am not sure exactly how these work, but it may be trying to download parts of the iso from different places and that is why you are ending up with rar files.

Hope this helps, Keep me posted.