I want to build a totally new PC to replace the one I built over 2 years ago. I don't want to use windows 8 as I tried it for a month and didn't get on with it. I want to wipe the OS from my current PC. So I will have my original Windows 7 OEM OS spare. Will I be able to reactivate it by phone with Microsoft on my new PC build as I don't want to buy another Windows 7 licence?