I used to work at the computer labs of a couple of colleges so I've got quite a few stories.
I used to see lots of people come in, turn off the computer at the switch, sit there for a little while staring at the computer, turn it back on, wait for it to reboot, and then
use the computer because they were too stupid to notice the screen saver. If they'd have just wiggled the mouse or hit a key they would have saved time and wouldn't have shut down the computer improperly. I guess the blinking cursor in the upper left corner of the screen wasn't enough of a hint that the computer was already on? There were a few people who I had to explain this to more than once.
Then there was the guy who inserted his disk in the gap between the two floppy drives. We had to take the computer apart to get his disk out.
I also used to get calls from the other labs like this:
User on phone: "I'm having trouble with the computer."
Me: "OK. Can you be more specific?"
U: "Nothing is on the screen."
M: "Is the computer turned on?"
U: "Yes, the light is on."
M: (from experience) "Which light?"
U: "The one at the bottom of the screen."
M: "That's the monitor. Is the computer
U: "What's that?"
M: "It's the box that's attached to the monitor."
U: "Oh, you mean the CPU." (a little knowledge is a dangerous thing)
M: "That's the computer. So, is it on?"
U: "Oh. How do I tell?"
M: <sigh> "Is the power light on?"
U: "Umm... I don't see any light."
M: "OK. Then the computer is off."
M: "Turn it on."
U: "Oh. OK. ... Oh! Now it's working. Thank you so much!"
I can't imagine what these people do when faced with a VCR.
Then there were the people who you'd try to explain to them how to do something, but they'd keep jumping ahead and guessing (wrongly) about what the next step was over and over, causing me to have to add more steps to undo the previous errors. After a while you just have to say, "Stop guessing and only do what I say to do. You're making this take longer and other people here need help too!" Gah!
I also worked tech support for a software company for a while and got calls that went like this:
User: "So I did that and nothing happened."
Me: "OK, what's on the screen?"
Me: "Wait. Nothing?"
Me: "No text or anything?"
User: "Well, the loading message is still up there, but nothing new is on the screen."
Me: Thinking to myself, "That's a mighty strange definition of 'nothing' you've got there," saying, "OK, you have to wait for it to finish loading first."
I've also had people yell at me and threaten to sue the company I worked for because the software they bought, which they could try ahead of time as a fully functional free nearly unlimited use demo, didn't do what they wanted. Duh! Maybe you should make sure it does what you want before
you buy it?!? I even had one person threaten us with a lawsuit over problems caused by software some other company had written, apparently because our company's name was mentioned in the product since it used some of our code. How can you not understand that Company B is not responsible for Software A written by Company A? Oh, and did I mention it was porn downloading software?
On the personal side, it took me ages to teach my mom the difference between computer memory and hard drive space. "I think I need more memory because my computer is getting full." "Huh? ... Oh, you mean your hard drive is getting full. For the millionth time, mom, that's not memory, that's hard drive space."
I also just had to explain to my new roommate that his ISP was not AOL, he was just using the AOL browser and his ISP was actually Comcast (which he both knew and somehow didn't know.) "But it says AOL on the screen. Comcast is just my internet." I'm currently attempting to slowly ween him off of the AOL browser.
I swear, this is just a tiny fraction of the many, many incidents I've encountered in my lifetime.
The difference between intelligence and stupidity is that intelligence has its limits.