What is this hellish "windows.old" folder in Windows 10?

Question

Windows

I first encountered the new Windows 10 system and just connected it to the Internet, so it immediately started downloading everything from everywhere and updated to version 1709, after which it backed up the old version in the "windows.old" folder. And so I suddenly decided to get rid of this huge folder, and problems started ... I started deleting it in the usual way via shift + del, but a lot was not deleted, it referred to a denied access. I read about this folder on the Internet and everywhere they write that it should be deleted through Disk Cleanup, and indeed cleaning more or less helped, but there were still about a dozen empty folders that didn’t give in at all, and then I remembered that sometimes this the regular program Chkdsk helps, that the file system may have bugged. I booted from LiveCD, it will run a check, and after all this, a lot of files appeared in the folder for a couple of gigs, and lo and behold, she allowed herself to be completely deleted, and that's when it started... system and enter a password, as soon as I select a user, it instantly hides it and shows the clock. I thought that the problem was in the password and decided to reset it via LiveCD, but it didn’t get better, after that I didn’t even get to the greeting, but the “Wait” message hung endlessly on a blue background. Only the restore point helped, but these restores do not inspire confidence and now I'm thinking of reinstalling the system completely. So I want to ask what kind of folder is this strange? Why is it so difficult to make it? And where did I go wrong? After rebooting the system, at the moment of greeting, it threw a message about an incorrect password every other time and I could not log in and enter the password, as soon as I select a user, it instantly hides it and shows the clock. I thought that the problem was in the password and decided to reset it via LiveCD, but it didn’t get better, after that I didn’t even get to the greeting, but the “Wait” message hung endlessly on a blue background. Only the restore point helped, but these restores do not inspire confidence and now I'm thinking of reinstalling the system completely. So I want to ask what kind of folder is this strange? Why is it so difficult to make it? And where did I go wrong? After rebooting the system, at the moment of greeting, it threw a message about an incorrect password every other time and I could not log in and enter the password, as soon as I select a user, it instantly hides it and shows the clock. I thought that the problem was in the password and decided to reset it via LiveCD, but it didn’t get better, after that I didn’t even get to the greeting, but the “Wait” message hung endlessly on a blue background. Only the restore point helped, but these restores do not inspire confidence and now I'm thinking of reinstalling the system completely. So I want to ask what kind of folder is this strange? Why is it so difficult to make it? And where did I go wrong? I thought that the problem was in the password and decided to reset it via LiveCD, but it didn’t get better, after that I didn’t even get to the greeting, but the “Wait” message hung endlessly on a blue background. Only the restore point helped, but these restores do not inspire confidence and now I'm thinking of reinstalling the system completely. So I want to ask what kind of folder is this strange? Why is it so difficult to make it? And where did I go wrong? I thought that the problem was in the password and decided to reset it via LiveCD, but it didn’t get better, after that I didn’t even get to the greeting, but the “Wait” message hung endlessly on a blue background. Only the restore point helped, but these restores do not inspire confidence and now I'm thinking of reinstalling the system completely. So I want to ask what kind of folder is this strange? Why is it so difficult to make it? And where did I go wrong?

Answer 1

What is this hellish "windows.old" folder in Windows 10?

This is a system folder.

And so I suddenly decided to get rid of this huge folder, and problems rushed ..

Get rid of system folders through regular disk cleanup mechanisms. Delete through the explorer is not the best solution, there will most likely be a bunch of hardlinks, estimate the size through the explorer - the same story.

Only the restore point helped, but these restores do not inspire confidence and now I'm thinking of reinstalling the system completely.

Restore points are needed not for suggestion, but for system rollback. Used to create an exact copy of the system at a point in time. Rearranging the system, with a restore point, is, to put it mildly, unwise.

So I want to ask what kind of folder is this strange? Why is it so difficult to make it?

The folder is system, it is difficult to make it so that it takes up little space, and at the same time it was easy to roll back to the previous version.

And where did I go wrong?

You made a mistake when you started deleting the system folder through Explorer.

Answer 2

I'll add to Artem's answer : windows.old is the previous version of your system.
Most likely, the situation arose when installing the next major update: in this case, windows makes it possible to roll back to the previous version.
The folder is deleted automatically - or - you can delete it via
(drive properties) -> (general) -> (disk cleanup) -> (clean up system files).
There, in the list for cleaning, you will see "Previous versions of Windows" and "Cleaning updates" with an estimate of their volume, and, as a rule, incorrect - again, Artem wrote everything, and disk cleaner, apparently, does not know how to work with links correctly.
Through this interface, it is relatively safe to delete such things.