Download Assassinations via a download plugin(Flashget from
http://flashget.com works for me), then unpack Assassinations_v5.exe and Readme-Assassinations.txt from Assassinations_v5.zip via Winzip(if you have Total Commander - and I recommend this program - it will allow you to get into the archive automatically), then, whenever you are ready to install the mod, click Assassinations_v5.exe twice, and the mod will install.