^^to remove windows 8,simply install any other OS by formatting the partition on which win 8 was installed.if you are dual booting and would like to simply go back to the other OS permanently,first install easyBCD and cross out win 8 from your bootloader,then just boot into your other os(most probably win 7) and use the windows partition tools to format the partition on which win 8 was installed.
easyBCD-http://www.softpedia.com/get/System/OS-Enhancements/EasyBCD.shtml