you have to use the same product key..
if you formatted it no, you would have to reinstall the old OS again
Not unless you install a Windows or Mac operating system onto your console, in which case all you have to do is uninstall and reinstall it because the virus can't be saved on the PS3 harddrive.
If you operating system is unbootable, then the safest option is to reformat and reinstall.
recovery
Reinstall the operating system.
To remove Smoothwall, you'll need to access the system where it's installed. First, ensure you have backups of any important data, as the removal process will erase configurations. You can typically uninstall it by booting from a different operating system installation medium (like a live USB) and then formatting the disk or partition where Smoothwall is installed. After that, you can reinstall your desired operating system.
Recovery ~tekno
Use system restore, failing that reinstall M.E.
you have to restart your whole operating system and then it will revert to the old operating system. you have to restart your whole operating system and then it will revert to the old operating system.
It in UNIX the GUI is separate from the operating system itself. You can uninstall the GUI and still have a completely working UNIX system.
To uninstall macOS X Lion, you typically need to erase the hard drive and reinstall the operating system. Start by restarting your Mac and holding down Command + R to boot into Recovery Mode. From there, use Disk Utility to erase the Macintosh HD or the relevant partition. After erasing, you can reinstall macOS from the Recovery menu by selecting "Reinstall macOS." Make sure to back up any important data before proceeding, as this process will delete all information on the drive.
Reinstall your operating system. You can't set it, but it will change.