So when i tried to start up my pc today, i tried to install windows xp ( Compatibility issues) But it my disc got a read error. so i tried to install a pirated copy of windows 7 ( to fix the boot manager ) , then that worked fine, but once i let the pc restart for the first time, required in setup, it just kept going to the xp installation and says insert the xp disc, wich didn't work. so basically i need to know how to select a different OS to boot up with, and there's no option to select witch one i want to boot up with. PLEASE HELP!!!!