Im with ND...hard to tell though. To be honest though mate...if you havent used booleans much...I would steer clear of them until your comfortable using them. They can be tricky to use as Im sure a lot of people here will tell you. Have a look for ctbram's tut on how to create holes...a lot easier and less mesh editing. The way you place a boolean is critical to avoid too many added divisions.

cheers bullet