A rar file is just another file compression system like .zip files. You will need to find a rar reader program that can un-rar them into a folder on your desktop. Winrar has a trial version
http://www.rarlab.com/download.htm <- there and you can also use the rar reader for ppc's "pocket rar" attached to this post. To use Pocket Rar you will have to install it on your 6800 and then save the rom and radio that you find in rar format to a card and un-rar them into a folder on the card and transfer them to your PC via card reader. It's much easier to just use Win Rar. Dont forget to hit the thanks button for all the people helping you today! Good Luck.