Format laptop on windows 8.1?

We wanted to format my laptop because I've pulled so much trash over the years and everything is just full of pop-ups and slow.

Now the problem is that when I go to the disk and try to format it, an error message comes out (see picture)

Laptop has Windows 8.1

After that it no longer starts, a new installation is made from an installation medium.

And to save you the grief, the system refuses…

Do you want to format the hard drive where your system is on? After that, you no longer have 8.1, then you have nothing, then your laptop is PLATT. You can only do this anew by creating a data medium e.g. To install Windows 10 or 8.1 again. Then if you are booted from it choose "Install Now" and then custom and then just delete everything and reinstall Windows. If you don't know exactly what you're going to do with it and how to do it, look e.g. There are enough instructions on the YouTube channel "Tuhl Teim DE".

You can't format the data carrier because your system is on it.

Many thanks for the answer.

You're welcome!