PIMSY downloads the same on Windows 8 as other versions. However, some clients have run into an error box saying "It is not recommended to run/download." You need to click "More Info" and then click the box that comes up "Run anyway." This will allow PIMSY to download onto your computer and run normally.
Please refer to THIS ARTICLE for more information regarding PIMSY installs on various Windows versions.
If you cannot find what you need in this article, please contact Support (email) or call 877.334.8512 ext. 3.