1. Stick in a USB boot drive and re-boot. You will get the boot screen and would be able to re-install another OS.
2. If OpenELEC bypasses the boot selection, then try hitting the keys F8 / F9 / F12 during booting which would bring up the Bios boot menu.
(This key combo would depend on your motherboard make/model)
On the Bios setup, select the boot sequence as USB being the first, and re-boot.
btw if OpenElec is installed, you cannot get to a "normal windows state" unless you install windows.