Applications on the laptop do not start, hard drive is defective?

Moin, start on the laptop no more applications, start up and work, but as soon as you want to open folder, Explorer, Settings, etc., it shows no reaction and hangs up eventually. Has happened from one day to the next. Is the hard drive in the bucket? Do you have any advice? Rebuild Windows, would this really help with such a problem? I'm currently at a loss.

I would spontaneously try to start the computer with a Linux live usb stick, if that works then step by step to exclude a hardware defect.

So a review of memory with Memtest

Reading the SMART data of the hard disk

A stress test of the CPU

A detailed check for malware

And if all this works and so no errors show then you should back up the data and reinstall Windows.

If the hardware turns out to be defective then also secure data (if possible) and think about a new notebook.

In the case of malicious software but in any case delete the affected data, secure unaffected data and have the backup checked a second time.

I thought so too, but then he certainly broke a simple guide to create a stick.

Boot your system with an installation media and perform a system recovery under Computer Repair Options / Troubleshooting.

Sometimes, with such a quirk, a restart can help (in the shutdown menu, select "Restart").

If the time at which the quirk occurred was not that long ago that there's still a suitable restore point, a system restore in Safe Mode can help.

There are different ways to get into safe mode with Win8.1.
Here is a possibility:

More instructions on YouTube.