So I have always gotten jokes. A friend told me his favorite and i just don't understand it. I did a web search and found variants but no explanation why it's funny or what it means. Can you help?

It was nothing to do with Windows, it's a sorta joke where the person telling the joke is trying to use logic to compare 2 different things, with humorous results.
A better example is an old Norm Mcdonald (I think) joke, I'll post it below.
A guy sees his new neighbor out in his backyard, so he decides to get acquainted. After introductions, he asks the new neighbor what he does for a living.
The new neighbor says, "I'm a professor." The first neighbor then asks, "Oh yeah, what do you teach?"
"Logic," the professor reponds.
"What is that?" the neighbor inquires.
"Well, let me see if I can give you an example...you have a dog, right?"
"Yeah, that's right," neighbor #1 responds.
"And you have children too, right?" says the professor.
"Wow, right again!" exclaims the neighbor.
"So, then you must be married and that would make you a heterosexual, right?'' proclaims the professor.
"Unbelievable, you're absolutely correct. How do you know all this about me?"
"Well," the professor says, "I observed there was a dog house in your backyard, so you must have a dog. I also saw bicycles next to your garage, so you must have children. And if you have children, you are probably married and if your married, you are most likely heterosexual... it was all logical!"
The next afternoon, the neighbor runs into his old friend. His friend asks if he has met the new neighbor. The man says that he met him yesterday.
"What's he like?"
"Well," the man says, "he's nice and he is a professor of logic."
"Oh," says the friend, "what's logic?"
"Maybe I can give you an example. Do you have a dog house?"
"Why, no, I do not," responds the friend.
"Well, then," proclaims the man, "that means you're gay!"
- Great example!
- The real joke is always in the comm…--
  We don't do that here, sorry, I forgot
  
  But you added clutter to the comments all the same. Good job.
  
  https://media.tenor.com/GUyFGPRElJMAAAAC/blazing-saddles-watch-your-ass.gif

I would argue that:
This is not actually a joke in the strict sense of the word. There is no punchline. The humor is entirely in the context.
Your friend does not understand any of this and is just repeating the "joke" because other people laughed about it at some point. It has nothing to do with the Windows operating system, so if that was part of his explanation he is probably just making shit up to cover his own ignorance.
- Interesting take, but I don't think I can agree. While typical American humor is often based on question-answer/punchline structure, many comedians managed to excel at purposefully breaking it.
  Think about Joe Cera, John Wilson, Nathan Fielder even Jon Benjamin or David Cross. They are all very funny (it the audience that vibes with their style), yet usually avoid the idea of buildup-punchline.
  For a more universal surreal humor you need look no further than the granddaddies of the entire school: The Monty Python crew. They often went out of their way to ridicule the idea of a punchline and were/are some of the funniest people in history.
  (You could always argue that humor does not equal jokes I guess, but these were just my 2 cents)
  
  You could always argue that humor does not equal jokes I guess, but these were just my 2 cents
  That was exactly my main point; but thanks for sharing your 2 cents anyway, they were still interesting.

This reminds me of a similar joke:
Sharks can swim faster than humans. But humans can run faster than sharks. So in a triathlon, it all comes down to who can bike the fastest
- Now THAT'S a joke!

https://knowyourmeme.com/photos/2645809-diogenes-posting
- The poster commenting on mobile homes forgets that he’s not saying that all houses can’t move, just that if any houses can’t move, the windows must not be a factor
  Diogenes would have fucked that dude up
  
  All houses can move.
  Some only once.
  Source: Californian
- It's much funnier in the context of dunking on Plato
- Damn, lol. He might need to show this to his friend also.

I guess the joke is that someone is using logic and reasoning to figure out what propels a car as though it was some great mystery that needed to be analyzed and thought about. I don't think it's very funny and it could have also been your friend's delivery.
- Yeah to me it reads like an example of stupid genius. Like you're smart enough to be able to logically equate similarities between different things while trying to use Aristotelian logic to uncover a fundamental truth about something.
  Oh in this case like you said, what makes the car go. And the idea is let's find other things that also have similarities with cars and see if we can figure out what makes the car go based off of these similarities, and in this specific case we're looking at windows and since cars go and they have Windows but houses don't go and they also have Windows then it can't be the windows that make the car go.
  But it's definitely one of those things that would only be funny in context of somebody mentally reasoning through this in situ and coming to this conclusion by their own cognitive processes.
  Of course, explaining a joke doesn't make it funny and if you have to explain a joke then it wasn't funny to begin with so yeah.
  It's kind of like the time I told a female friend, that I wasn't dating, that, "if I didn't like the way she sucked my dick then she wouldn't like the way I ate her pussy". It made everybody laugh but none of you are going to find that funny.
  It's one of those things that sounds really bad by itself but in the situation it was hilarious and it was good-natured and only mildly offensive at the time.

I've heard this before, but more in the context of a proverb than a proper joke. As far as meaning, I think it's along the lines of "correlation doesn't equal causation," but not exactly.
- Yeh I think if he hadn't called it a "joke" the meaning would come more naturally but then again he explicitly said it's somehow got something to do with the operating system called windows so WTF?

Reminds me of this one :
"Honey, close the window, it's raining outside."
...
"Love, I did close the window, but it's still raining outside."

This might not be what your friend is going for, but I smirked slightly and this is how I interpret it:
I particularly like jokes that take something absurd and launder it through the structure of things that do make sense. Everything in your friend's joke is factually true. It's structured as a logically consistent argument.
And yet it is completely nonsensical. No one has ever thought that windows make something move. It invoked a slightly confused response in me, which is why I found it funny.
It's not a great joke, but I might tell it to feel out someone's sense of humor plus whether they pick up on that I'm doing so. I think the analogy to Windows makes it a weaker joke, but I would give that as an explanation just to mess with someone a little.
- That DOES sound like him
  
  If he's someone that's normally good at being funny - that is good at finding humorous observations and wording things that get people to laugh - then I'd say he's messing with you.
  I would mess with him right back by acting like I'm very seriously trying to understanding the joke and ask increasingly dumb questions until he realizes that yes, I knew exactly what he was doing. Or a knowing smirk if that's too much.
  (Yes this comment is very revealing about my childhood)
- Yeah, it made me think of my mother's favourite joke, which is completely bizarre:
  What's the difference between a blackbird? Both legs are the same length, especially the left one.
  🤷‍♀️
  
  Time flies like an arrow; fruit flies like a banana. - Groucho Marx

The humor comes from the unexpected final line. It's what's sometimes called an anti-joke, where instead of a punchline the final line is so banal as to be ridiculous, and that unexpected banality is the source of the humor.
- I love anti-jokes, but it's hard to enjoy them if you're expecting an anti-joke, which makes looking up anti-jokes really unsatisfying.
- Great way of thinking about it.
- A textbook example of this is Norm MacDonald roasting Bob Saget.

The closest example of similar humor I can think of is in Monty Python and the Holy Grail, during the trial of trying to figure out if the woman is a witch. The scientist is there to settle it for the peons, and uses "logic" to solve the problem of whether she is a witch. Ultimately they decide that if she weighs the same as a duck, she must be made of wood, which floats on water, and therefore a witch. It's a series of nonsensical correlations misconstrued as fact, and it's funny because we the viewers understand the absurdity of it.
I think it's more a bit of wordplay than a joke exactly, but that your friend said is in the same vein. What on earth makes cars go? Well it can't be windows, can it? Houses have windows and they don't go at all! Whether you find that funny is obviously subjective but I also think delivery and conversational context are very important for humor like this.

I am so confused right now. I don't see the joke written down anywhere. The post just links to an AI generated looking image of a woman in a red dress sitting on a red car in front of a building. Is that the joke itself?
- Are you also on kbin? Kbin post images are sort of their own joke, unfortunately.
  
  I am not
- Sorry the joke is in bold. It's about cars and windows.
- AI generated image of a car parked in front of a building. I got the woman for free, because SkyNet.

I'd say the joke is probably that you are logically deducting something thats already obvious to everyone, portraying logicians as people that are far removed from reality
- Yeah, that'd be my read.
- deducing, not deducting. Also, you seem to be talking about the joke from the comments. And the joke from the comments makes fun of the man misapplying logic rather than making fun of the logician.
  
  Nope, talking about the joke in the post.

I saw that used as a parody of how presocratic philosophers sound. It has nothing to do with the OS.
- But but the presocratics didn't have cars! /s

Not necessarly. Maybe the house has something the car does not that is preventing the windows from working.

I can't recall correctly but I think there was a similar one with alcohol. Someone that used to mix alcohol with other drinks. In the end he always ended up drunk so he decided to stop mixing it.

Reminds me of the Seinfeld New Yorker comic episode

All I get is that if two things have the same feature and one moves but the other doesn't, then what causes the movement isn't that feature.
Here I guess it means Windows isn't the reason anything moves forward, aka progress, but if there is more meaning to it I'm not getting it

I think its just a reference to an old shitpost, of which the humor derives from absurdity.

Something has to be the reason the car can move, and it can't be the windows because houses have windows and they don't move.
- No, it's different kinds of windows
  
  No it depends on their relative alignment