Question: I have a HP ProBook with Windows 10.

My keyboard just started acting super strange. When I press certain keys (shift, arrow keys, etc.), it acts weird; however, all the letter and number keys work fine.

I went to a laptop repair shop today and they said it seems to be a software problem.

They advised me to install Windows 7 instead of Windows 10 because they thought the keyboard driver in Windows 10 is defect or not compatible with my computer which came with Windows 7 pre-installed.

The weird thing is that it worked for a long time without any problems, but suddenly it stopped working. I had my computer turned off for some days and suddenly, the keyboard was back to normal without any problems. But it lasted only for a couple hours.

I have tried to change keyboard input language, and it seems to change the behavior of the keys; however, it is still not as it is supposed to be.

I have tried reinstalling drivers, but it says that it already has the most up to date drivers installed.

What can I do to find out what's wrong? And what can I do to repair it? Since it seems to not work to simply replace the keyboard, I have really no idea what to do.

I don't have a Windows 7 CD, so I don't know how to downgrade from Windows 10 to Windows 7.

Edit
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When I press SHIFT, my computer will automatically go one line down and highlight, so it seems that it presses the down arrow key while it holds the shift button.

If I press right arrow key, the screen rotates just like if I press ALT GR + RIGHT on a normal computer.

If I press CTRL in a browser window, it zooms out, so it indicates that the minus/hyphen key is being pressed.

I have checked on-screen keyboard, and it seems no keys are actually being pressed, so I don't know why it acts like this.

And as previously mentioned, some of the keys' strange behavior change to another strange behavior if I use another keyboard input language.

Answer: 
Try a USB keyboard and also try whether the issue is reproducible. If the issue is not reproducible, disable the laptop keyboard and use the USB.

If the issue is also happening on the USB keyboard check that:

1. The Windows Speech Recognition is turned off
2. Sticky Keys is turned off
maybe its a little late, I started having this issues too. It was a Windows update that was causing this. Uninstalled it and everything back to normal. Hope it helps.