If you boot your PC and in the UEFI BIOS your drive with Windows is listed first in the boot order, the PC will boot your Windows as usual.
You must therefore go into the UEFI BIOS during the boot process and either change the order or select the device to be booted directly. The key you use to enter the UEFI BIOS (in my case F2 or DEL or F8 ) often varies. However, it should be displayed briefly on the screen.
edlin
@dibl: Da er den win32diskimager verwendet hat, gehe ich mal davon aus, dass er sonst Windows nutzt und mit dd nicht soviel anfangen kann.