So I am upgrading from an off the shelf acer desktop PC to a custom build one with PCS and noticed the installation of windows 10 adds almost £100 to the order. Now i have windows 10 already installed on my acer desktop and have made a USB bootable drive with windows 10 on it that i used to upgrade an old laptop from win 7 to windows 10, and have even used it to reinstall windows on a spare dell desktop that had no OS on it before for testing purposes. Is it possible I can use this to install genuine windows on my custom built PCS machine? the reason being as my current built just so happens to be £100 over budget and not paying an additional fee for windows would allow me to be within budget. Has anyone tried the setup before as I don't see the need to pay for windows 10 again when I have already done so with my other desktop PC