Whats a free lightweight unpacker for RAWs?

Lately ive been getting into the fantastic world of Mount and Blade modding. Unfortunately a lot of the mods are packed as RAR files. Windows can handle ZIP files without outside help, but it seems rar files will require me to install something. THis is annoying because I try to keep my selection of software as small as possible.

Are there any RAR unpackers that operate out of a single exe the same way sumatra works for PDFs? Or failing that is there a really streamlined unpacker that doesn't bog down the system or try to install other crap in the background? I had bad experiences with WinRAR itself, first came the yahoo toolbar then it never ceased to bug me about registering. Even when I wasn't using it...

7-zip. The standard in archival utilities for Windows.