This was done on a Sony Vaio laptop, model VGN-NR180E. Somebody had done a clean install of a pirated copy of Windows 7 Ultimate. The laptop came originally with Windows Vista Home Premium. Owner wanted to sell it but first get rid of the pirated OS. No recovery disks were available. The recovery environment partition was, fortunately, intact. How to invoke it without recovery disks?

Nothing could be easier. Just order the recovery disks. Just kidding. But before I tell you what to do, let me disclaim it: Make sure you don’t need the data in your current working partition (Or you have backed up the data/files/documents you need from it), because if something goes wrong you might not be able to access the data anymore, and if everything goes the way it should, you CERTAINLY WON’T be able to access your data when done, since the purpose of using the recovery partition is to restore the computer to factory state, thus irreversibly and destructively overwriting everything in your current system partition.

Open an elevated command prompt, type diskpart and press enter. Now assign the hidden recovery partition a letter by using the assign command. Good. Now make it the active partition with the active command. Google how to do these, as I don’t want to make this a tutorial about the diskpart command.

Reboot the computer and it will boot to the Vaio recovery environment. From there you can make the appropriate menu selections to get the back-to-factory-state restoring process going.

Hope this helps.