Nah, forget about chankast. Spend some time to learn how to use a PC and try the emulator after that. If you still want to try you should read the stickies and the Chankast manual. Rar files are like zip files, you'll need winrar to decompress them.
I like powerarchiver, it's cheaper than both winzip and winrar, and overall nicer IMO - and there are several others too which are free: 7zip, zip genius, izarc, ultimatezip...