Also if your computer is older and still using a hard drive you should upgrade to an SSD after upgrading to windows 10 to make it run faster. You can get them for $100 or less and all you have to do is mirror your hard drive to the new SSD, then you just swap them out. It's like going from a worn out slant 6 to a new hellcat, its the best thing you can do to an older computer.

Find out how big your hard drive is, 240gig, 512 etc. Buy a same size or larger SSD, then buy a USB to SATA cable to plug the new SSD into the USB port and follow this