Decompression help please!

I can't seem to decompress the rar's for this game. Winrar and winace tell me it uses unknown methods so it can't be decompressed. I know I should just have to begin decomp on 1 volume and it should proceed to do them all, but it jsut won't work for me. Please help as I've wanted this game for a long time. Thanks in advance.
You probably just need the latest version of WinRAR. Newer versions of the compressor are not compatible with the older versions.
Kind of like forcing you to upgrade
You're not stoopid

It actually happened to me a while ago, and it took me a while to figure out too