If you delete the old Windows files, you could free up the disk space up to 20 to 25 GB. So, you might get the running out of the disk space error message. Due to presence of windows old files, the size of installation space increases significantly. When you upgrade the PC to Windows 10, it stores and backs up all the older files from the previous version of OS so that you can revert all the changes and downgrade your PC any time by uninstalling Windows 10 OS. This error message creates a problem to Windows 10 users as their PC gets slower due to unavailability of enough free space on installation drive, i.e. Windows 10 users can get the running out of disk space alert message after updating the PC from Windows 7 and Windows 8.1.
