Every window I've ever had that had this issue was because of a flashing issue above the window or somewhere above and around the window.

Had the same issue in our old house long time ago, ended up not being the window but the siding 'leaking' when rain was pushing against it.

Since water comes from the outside to the inside...we need to see the outside. As the comment above, you can install flashing under the lip of the vinyl siding to coax the water outward, or you can fix the actual problem. Many times vinyl siding is just hiding the real issue. You have an outside seal that has failed somehow. If this is a new thing and it is just a failed seal, it should be simple to fix. If there is bad wood or a structural defect under the siding....that can get a bit more complex. either way, water is your enemy, and you need to get it addressed ASAP. The longer you go, the more expensive it will be.

Take a picture of the outside wall and window to give better idea of what's going on. It's definitely a outside issue.

Am I the only one who thought he needed computer help?

Not to derail this thread too much, but I had a similar but opposite reaction years ago. I went to a party my wife was attending with her coworkers around 1991 or 1992 I believe. Anyways, we were talking about what we all do for a living. There was this petite lady, maybe 5'-2" and 120 lbs soaking wet that was explaining what she did. She explained that she installs windows pretty much all day long and it's basically all she does at work. I'm like trying to figure out how she can even manage to climb a ladder let alone carry a large piece of glass with wooden framing all around it. I was very impressed to say the least. They then all chuckled and explained to me it was a software program...Windows 3.1. LOL! I was still living in a DOS 6.22 world apparently.

It is likely a caulking issue... either around the window moulding outside or where the siding meets the woodwork somewhere above the window (or some other architectural feature above the problem window).

That’s not a busted piece of siding, that’s a rain cap for where the two windows meet in the middle. And 7 laps above the middle is just where two separate pieces of siding meet. I would bet that the rain is entering behind the siding above the windows. The flashing around the window is compromised somewhere. Not the easiest thing to fix unless your pretty handy.

Call a local home improvement contractor who specializes in roofing and siding. We can’t see how your vinyl window was installed from the pictures you provided. As others said lack of aluminum drip cap might be a cause. Also there is no vinyl J channel around the window frame in the pics. Does the window have an integrated J channel built into the frame? If it’s damaged at the head of the window, This could also be the cause. Vinyl siding is incredibly easy to work with. It Doesn’t look like you need to replace any siding at all. You need theinstallation details inspected for defects or missing components. It shouldn’t be very expensive to remedy the issue.

You are correct. That’s not broken siding it’s actually what is called a mull strip cap. When manufacturers join two or more windows they install a mull strip cap over them where they are joined. Basically it covers the hollow vertical vinyl piece between the two windows.
Lack of alum. head flashing seems to be the most likely cause.
Be very glad it’s in a vinyl siding area if it was stucco or Stone it would be quite a bit harder to repair.
Did you buy your home new? If so call your builder ASAP. New construction latent defect laws vary by state but 7-12 years are common in my area.

Please read my first post.
Also It’s hard to tell from the pic but it looks like the siding is caulked directly into the integrated J channel at the head of the window. The fix may be as simple as recaulking with a quality silicone.

This probably isn’t going to help the leak issue but the mull strip cap looks like it isn’t locked in the channel (green line)

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The builders look like they cut some corners there. There is no J channel along the top of that window. Water is just sliding into your house along the top, underneath the siding. There should be a transition piece under the last siding piece that is shaped like a J and hangs over the front edge of the window. With a J channel on top, any water collected in that channel runs out and down either side of the window and drips to the ground.
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Shouldn't be difficult at all for someone that does siding for a living to add the piece(s) that are missing.

You could jam some silicone in there but trust me, it will eventually leak again.

The windows most likely have an integral receiving channel which simplifies window installations and gets rid of the conspicuous J-channels

It's obvious that is not the case here unless it's severely damaged... (Water along top of the window inside his house.). I guess that's possible but you are looking at removing a lot to repair a window with that type of damage.

You sure about that?

Like I said, it's not likely that the top of the window is damaged. That COULD be but it is much more likely that the builders missed something over the window failing. To know for certain, lets have the homeowner rip that piece of siding off the house.

Anything that requires disassembling pieces of a house on a ladder is best left to professionals.

House was built in 2005, I’d gather if something was missed they would have seen an issue years ago. I’d bet that the window itself needs to be re-flashed and taped to the substrate beneath the siding

I don't disagree. Very possible. It's also possible that the builders did every single thing correctly, the window shifted because of years of ice freezing/thawing, and now there is a way for water to get in. It happens.

And to the OP, removing vinyl siding isn’t as easy as you might think. Getting it off is somewhat easy with a tool they sell at home improvement stores, now getting it back on is the not so easy part.

Think of vinyl siding as decoration for your house. Sure, it uses J channel around the window to divert water but that’s not what keeps it out. The mastic or flashing under the siding at the window has failed.

The siding around the window needs to be removed or lifted up to get at the issue.

There’s weep holes built into the siding to let condensation and rain drain out from behind....the Tyvek and flashing keeps the water out of your house.

Read the install instructions for any window and you’ll have a good idea of what’s going on.

He’s correct

I’m not even sure it’s actually flashed otherwise you’d see the edge of it in the channel on top of window, and even then what would prevent water from filling the channel and running back under it and into the house. Normally there’s a drip cap the runs across the entire top of window that gets sealed to the sheathing. If water gets thru siding it will run down wall come out over drip cap and down the face of the window.

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If it never leaked for 14 years and this is completely new, most likely it’s failed caulk/silicone or a deterioration of the vinyl windows integrated J channel. I’ve seen vinyl “welds” fail where the various pieces are bonded to each other. UV damage sometime is the cause.
Also keep in mind that weather has become much more extreme than it used to be. Most areas get 100 year storms every year or every few years now. Unless your house is built like a boat water will find a way in during heavy rain and very high winds.
OP please Keep us posted.
I’m curious to see what you find.

Call a contractor. The only real way to fix it is by removing the siding from above the window and re-flashing it. Removing siding is a pain and once it’s been on a house in the sun and weathered it becomes brittle. I moonlighted for a buddy that ran a siding company for a couple of years and wouldn’t attempt to do it myself. Actually we both know I would because I’m too cheap to pay someone else but that’s just me. LOL

I have seen this before and it was the nailing fin cracked from the top of window probably from the window being nailed balls tight to the wall and had no give for the house flexing. This allows water to sit in integrated channel and seep into the house. Builder should have used protecto-wrap on the nailing fins to prevent this from happening if the fin cracks. That and not nail to window so tight.

Best thing you can do here. Good luck, and let us know how it comes out. They likely just jammed it with caulk, and that eventually fails. A contractor should be able to fix it right at a reasonable price. Now go and play pinball.