Is not that it "slows down your computer" is that "skining" or putting another theme on your computer takes a lot of RAM, which is constantly running. If you have 2GB of RAM there is no problems in using WindowBlinds and any other program that allows you to skin your pc. But I also heard that WindowBlinds contains "a sponsor" which installs spyware or ad-ware on your pc. I'm not sure of that though.
