How to find out the operating system computer has

Depends on if you want to be nice to the guy you're selling it to.

There's a program called Derek's Boot-And-Nuke (commonly referred to by its initials, DBAN) that will totally annihilate everything on your hard drive, making sure nobody sneaky could ever get hold of your personal data. It's great for when you're selling a computer, but unfortunately it leaves the machine with a blank drive which may be troublesome if the buyer doesn't know how to install an operating system on their own.

If you feel like being nice, then look up the machine's documentation on the manufacturer's website. On newer computers they will often put the restore programs on a special partition on the hard drive, instead of giving you a physical disc. If this is the case, it will say somewhere in the documentation how to boot to that hidden partition.

If there is no recovery partition, then you are perfectly within your rights to download/burn a windows disc for yourself. Just be sure to use the product key on the bottom of your computer to prove you legally paid for windows.

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