Originally Posted by Matth

In general, only RAR will compress RAR, decompression is available on a free licence, compression is not.

7-Zip is my compression program of choice. Don't ask me to use RAR, I will not perpetuate a proprietary format - if you want me to compress a file, you can have it in zip, 7Z, or any other format with open/free compression. I don't do RAR, I don't do ACE.