Even "it's a mysterious black box that might work right if I keep smashing the buttons at random" is a model, just a poor and confused one. Literally not having a model about something would require knowing literally nothing about it, and today everyone knows at least a little about computers, even if that knowledge all came from movies.
This might sound like I'm just being pedantic, but it's also that I find "most people are stupid and have literally no mental models of computers" to be a harmful idea in many ways - it equates a "model" with a clear explicit model while entirely ignoring vague implicit models (that most of human thought probably consists of), it implies that anyone who doesn't have a store of specialized knowledge is stupid, and it ignores the value of experts familiarizing themselves with various folk models (e.g. folk models of security) that people hold about the domain.
Literally not having a model about something would require knowing literally nothing about it, and today everyone knows at least a little about computers, even if that knowledge all came from movies.
Even someone who has know knowledge about computer will use a mental model if he has to interact with a computer. It's likely that he will borrow a mental model from another field. He might try to treat the computer like a pet.
If people don't have any mental model in which to fit information they will ignore the information.
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.