Contact hp for a set of recovery discs or take it to a reputable computer repairer or look on piratebay or ebay or such like for recovery discs for your model no other model will work,however you may have a recovery partition tapping F10 on start up should get you there or F8,or install a version of linux,zorin is windows like

press f11 during bootup but before windows loads. read this link.
http://h10025.www1.hp.com/ewfrf/wc/docu...eWithoutWindows

http://h10025.www1.hp.com/ewfrf/wc/docu...n&product=95546

This will tell you what you need to do.
How did i find this? www.google.com