Don't clear the cmos, that is only as a last resort. It can be difficult to reset the bios to your specifications especially if you can't remember whether you use AHCI or IDE mode for the hdd.
If it hangs on the onbvoard vga, it could be a recent bios update or a reent driver update. You have to check the manufacturer website for the specific driver manufacturer of the onboard vga.
Assuming your OS is Winows 7 x64 (you can choose your Os from the dowload tab at the site - http://ca.asus.com/en/Motherboards/Intel_Socket_1155/P8Z77V/#download
Intel(R) Graphics Accelerator Driver V184.108.40.20612 for Windows 7 32bit & 64bit.