oem disc

My wife's desktop currently has a valid license for Windows 7 Home. When I upgrade that machine I want to go with Windows 10 Pro. There was another post that listed sources for paid OEM versions here: Win 10 Pro OEM sources * I'm confused about the difference between "retail" and "OEM." Her...

If I had a computer that I wanted to install or upgrade to Windows 7, could I use an OEM disc (such as this) to get Windows installed and activated? I have a feeling this is not the case, so would there be any other good ways to get Windows 7 (not Windows 10, I'm going for budget) activated...