Detailed Description and SymptomsThe RA-FTP Documentation provide instructions on how to create a Public/Private Key on a Unix/Linux box, since the utility comes standard with Unix/Linux.
The key generated can be used for Windows, but PuttyGen might be easier for Windows users.
SolutionLink to download PuttyGen:
http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html