You can usually unzip it with Win Zip I think. Mayeb check your options in WinZip so it does RAR files.
Or get Win Rar http://www.rarlab.com
which is free. Yes It says trial but the trial never ends It will just pop a window to nag you after 60 days are up. Just click it closed and keep going.
Also Win Rar lets you extract many files at once.
I prefer Win Rar myselfand it unzips many program types not just Rar files but Zips and many others also.