If you installed windows 8.1 and you tried anything but still couldn’t get rid of the folder Windows.old because you get an error saying that you should rename the files in order to be able to move/delete them and you can’t edit the too long name of the files, here is the solution:
1. Go to Control Panel – User Accounts and Family Safety – User Accounts – Manage another account – Add a new user in PC settings – Add an account and complete all the fields there. There is no need to verify the account just created, just restart the computer after you are done.
2. When you restart the computer, click on the arrow next to your profile and select the new account to sign in. After you are logged in with the new account go to the place where you have the Windows.old folder and move it on the desktop.
3. Restart the computer and this time log in with your old account. As you can see, the annoying Windows. old is no longer on the Desktop when you are logged in with your old account.
4. Go to Control Panel – User Accounts and Family Safety – Remove user accounts – Select the account you just created – Delete.
Now you got rid of those annoying read-only, hidden .DAT files from your Windows.old folder and you can enjoy your new windows 8.1!