Try switching to the Windows native audio driver and see if it makes a difference. If you get the same symptoms then probably not a driver issue.

1. Open the Device Manager (find it in the Control Panel, or type devmgmt.msc into the search box).
2. Expand the "Sound, video & game controllers" and right click on "Realtek High Definition Audio".
3. Select to "Update Driver Software".
4. Click on "Browse my computer for driver software".
5. Click "Let me pick from a list of drivers on my computer".
6. Put a check in the box "Show compatible hardware" if not already checked.
7. In the list of devices, click "High Definition Audio" (the native driver).
8. Click "Next".
9. On the Update Driver Warning box, click "Yes" (install the driver).
10. Restart the laptop if prompted. If not prompted, then no need to restart.
[To get back to the Realtek driver, do it again but reverse the names in steps 2 and 7.]

Thank you for replying.

I tried it, it still causes the same problem.

I think all the drivers have a problem, but in case I'm wrong what could be the cause of that if it's not the audio driver?

The expert on Windows installation, natakuc4 (Philip Yip), says that the Win10 upgrade retains the old drivers and that they conflict with the new ones. He says that to get 10 to work right, one has to do a clean RE-installation of 10 (after the upgrade) which eliminates the old drivers. His guide to doing that is

http://dellwindowsreinstallationguide.com/a-clean-install-of-windows/a-clean-install-of-windows-10/

That is way out of my area and I don't know if it will solve your problem. My personal solution would be to revert to the operation system in which audio had worked correctly.

Well, I tried to do a clean install of windows but it says that it cant install on a GPT partition... Even after I formatted it it still wouldn't work. :(

Does this mean that I have to reformat the entire drive or is there a way to change this just for the one partition?

Does this mean that I have to reformat the entire drive or is there a way to change this just for the one partition?

I referred this to Philip Yip. I think he will post here when he gets a chance.

Have you made the Bootable USB for the UEFI BIOS?

http://dellwindowsreinstallationguide.com/download-microsoft-windows-and-office/download-microsoft-windows/download-windows-10-oem-and-retail-iso/

If so use DiskPart Clean All before the Reinstallation:

http://dellwindowsreinstallationguide.com/cleaning-up-a-drive-format-vs-secure-wipe-ssd-and-hdd/

The bootable USB is set to MBR for BIOS or UEFI.

Now I see that rufus has an option for GPT for UEFI. Considering that my HDD is in GPT maybe I should have used that one? Or no...?

I don't understand why I should do a DiskPart Clean All. That won't change the GPT as far as I understand.

Yes select GPT when using Rufus, ignore the Diskpart for just now.

Yes, that fixed it, and the audio problem is also gone.

Have one question though:

I didn't enter a serial number during installation and then I did a win update and now I'm looking at the activation and it says that it's activated and the serial that's entered is almost the same as mine, just a few numbers at the end are different.

Is that like some kind of temporary serial, or is it replaced with a new one because it's now on win 10, or what?

Should I replaced with my original serial?

Its part of the new device based activation mechanism of Windows 10. During installation via the initial upgrade from Windows 7/8.1/10130 your systems hardware is scanned and a hardware profile is submitted to a Microsoft Product Activation server. You then get automatically activated.

Moreover once your device has been registered as a Windows 10 device during Reinstallation it will automatically submit the hardware profile again to the Microsoft Product Activation server which will recognize the hardware and automatically reactivate your system.

The Clean Reinstall as mentioned should perform much better than the Upgrade install.