Go to Home Despot, err Depot, and buy an outlet tester to see if the outlet is grounded first. If it is, then you can use an adapter safely. If it is not a grounded outlet, then an adapter won't do anything for you except make it easier to fry you or your computer. They're cheap and accurate. I also live in an old house with this problem and let me guess, you only have one outlet in each room! To my suprise, the 2-pronged outlet in my computer room was grounded.