First try re downloading impulse. you can save the install anywhere. when downloaded run it. the error message suggests that you have a FAULTY download. vista downloading files is the same as xp/w2000/me/98/95 and W7.
the unrar/zipping of mods you first have to find your mods directory with sins /options/mods/show mod path. write the path down. there will be two hidden folders in the path so you must also turn off the hide hidden/system folders option in explorer /tools/folder options.
then you unrar.zip the mod into the folder that you wrote down before.
by the way entrenchment has a seperate folder for mods to sins, and it appears that future versions of sins/entrenchment will have their own mods folders also do not mix up entrenchment mods and sins mods as they are not compatible
the main versions for sins are 1.05 (the only mod still for it is 7 deadly sins1.3 & 2.0), 1.13( pre-entrenchment beta), 1.15 (current), and entrenchment 1.01(current)
hope this helps
harpo