NewzTools is a graphical Windoze utility for reparing .rar files using .par file information and extracting the contents of the .rar archive. NewzToolz has separate functions for repairing archives, unpacking archives and decoding "yenc" encoded files. It also includes another program for combining several files into one. It is "freeware" but, under Windoze it will serve ads from TechSono now and then. Well worth it IMO.
It ran reasonably well on earlier versions of Wine but hangs both the program and wine in the 0.9.8 version.