New Hard Drive Questions

Okay, first my stupid question: I just replaced a hard drive in a laptop that died. Do I just toss out the old hard drive? It has nothing on it that I need (we were able to get everything off before it died), I just wasn't sure about disposal.

Second question: If I replace a hard drive in another old laptop I have, and I don't have the disks with the OS or any system recovery disks, does that mean I have to re-purchase the software in order to use the laptop again with the new HD? (This laptop was gifted to our office without the software, and I don't even know who the original owner was to contact them for the software.)

Thanks!

 

look on e-bay.

operating systems discs can be bought legally there.

the previous owner probably doesn't have any discs