Upgrading motherboard

I have a hp pavilion 7920 (http://h10025.www1.hp.com/ewfrf/wc/document?dlc=en&lc=en&product=59615&cc=us&dest_page=product&docname=bph06594) those are my specs and I want to upgrade my motherboard system. What do I need to know about upgrading it? I don’t know if it is an atx style or not. I’m not partial to intel or amd, but I do want to go at least a 3Ghz processor. Any help will be appreciated. Thanks.