ok, When you first turn on the computer, you should see (most likely) 2 options. you want the one that brings you to "Settup" or "BIOS" (This key is usually F2 or Delete. If you reach the Windows Loading Screen, its already passed.).
In the BIOS, you should be able to go to the last option (either through Tabs, or the bottom of the list on the left side of your screen.) Navigate to that option, and look for an option that says "Load Defaults". (if its not in the last tab/option, look through the other tabs, it should stick out like a sore thumb.) Once you select the option, just make sure you accept/agree and then restart the computer.