Just download the Windows 10 ISO from Microsoft and do an install. The install can even be done from a USB drive, don't need a CD. If the desktop isn't new enough to have UEFI the recent ISO's for Windows 10 will install using the key from your COA tag on the case. They've made it pretty easy to install it. Decide between an HDD (Hard Disk Drive) or an SSD (Solid State Drive). SSDs are significantly faster than HDDs and have a much longer life capacity due to having fewer moving parts. Because of these benefits, SSD drives are more expensive and come in smaller sizes. If money and storage are an issue, stick to the HDD. Physically swap your current drive with the SSD Now let's remove the old drive and install the SSD. 1. Turn the computer off and remove the back.