Minimal knowledge of Windows couldn't have hurt.
All of my courses had prerequisites listed in the booklets that advertised them. These were simple, and even logical: a basic knowledge of Windows and of Word (or any other word processing program). I always started teaching my classes with the assumption that my students knew how to find a document on their computer, to open one, to save one, and the like. I expected basic command of copying and pasting as well. But I rarely got them.
More often than not more than 50% of the people in my classes not only didn't know these basic skills, but hard hardly heard of them. Thus, asking them to find a document on the hard drive of their computer could mean taking ten minutes of class time instead of the intended thirty seconds. I usually prepared my material for ingenues, though one class was supposed to have experienced users. It didn't. I discovered that much of the time that was supposed to be devoted to learning to use the internet was spent on learning the basics of computer use. Figuring out where you've bookmarked a page really isn't difficult, but it helps to have prior knowledge in finding documents you've saved.
My most adamant instruction when teaching how to save a picture from the internet on one's hard drive was "remember where you've chosen to save it!". It was probably the instruction that was repeated most, and heeded least.
Go to: You mean you teach this stuff?