Windows 8 Windows 8.1 causes repeatedly blue screens

Hi,
in order to help you best we need to read the actual dump files. The thread linked to below has an app which will collect the data for you. All you need to do is zip it up and post:
Link Removed

In the meantime....

I can see from what you have already posted that your gpu driver is being blamed. Try removing the currently installed version using this app:
Display Driver Uninstaller (DDU) V15.7.5.2 Released. - Wagnardmobile Forum
It's best used in safe mode.

The above app will clean out anything left behind by previous driver installs leaving it clean for the new driver. Install the most recent update available for your machine:
Drivers - Download NVIDIA Drivers

Oh and I moved your thread to the correct section.

Thank you. According to Windows the most recent graphics driver (NVIDIA GeForce 7300 SE/7200 GS, 9.18.13.768) is installed. I uploaded my system info.

I noticed that playing HTML5 videos (like on youtube) doesn't work anymore, neither on Crome nor on Firefox.

Hi,
the above dump file has the following cause:

This bug check indicates that the DPC watchdog executed, either because it detected a single long-running deferred procedure call (DPC), or because the system spent a prolonged time at an interrupt request level (IRQL) of DISPATCH_LEVEL or above.

Click to expand...

Reference

I can see by the details within the dump file that the driver ha20x22k.sys was involved:
It's possible that it could be a different driver affecting the driver outlined above but if that does prove to be the case then testing will eventually bring the culprit to light. If the changes outlined below makes no difference to the bsods we'll use the driver verifer.
ha20x22k.sys Sat Dec 19 00:09:02 2015: Creative Technology Audigy. Please check for updates but if if non are available please re-install driver. When you re-install it please right-click start up exe and run as admin.

avgntflt.sys Wed Jan 13 17:40:59 2016: Avira AV, please remove until after troubleshooting has been completed. Avira has been known to cause issues in the past and we would ask that you just run on the default Defender for now as this is super stable.

Find command prompt, right click on it and run as administrator. Type:
sfc /scannow
press enter and await results

In the same command prompt and after the above scan has finished type:
dism /online /cleanup-image /restorehealth
Press enter and await results (longer this time).

If the first scan found files it could not repair but the second scan is successful, run the first scan again using the same command prompt box and this time it should repair the files found.

If the bsod's continue after making the above changes then please run the driver verifier. You will need to first create a recovery disk or USB in case the verifier causes a bsod loop on start up. You'll need the recovery disk/usb to boot into safe mode and then turn the verifier off:
Creating a USB recovery drive - Windows Help

Here is a short guide on running the verifer:
How do I fix a Blue Screen in Windows using Driver Verifier?

Post any new dump files.

Thanks. dism.exe found errors and fixed them, so I hope it will run stable from now on. However, I have a problem with my browsers (Firefox and Chrome) which I both have freshly installed. When I try to playback a video, for example on Youtube, I get the following message: "If playback doesn't begin shortly, try restarting your device." My internet connection is OK, because I can load other content without any problems.

Try updating your gpu driver.

If that doesn't help try some of the solutions offered in this thread.
http://answers.microsoft.com/en-us/...s/37bb4da8-8462-42be-ba2d-5dfda2f22a9e?page=2

I reinstalled Windows yesterday and it run stable until I installed the Sound Blaster Titanium X-Fi driver. How can I prevent Windows from automatically installing a driver?