hello, i have an early 2011 mbp MC700LL/A that i changed the hard drive on. when i put an original new snow leopard install cd to reinstall the os on the new hard drive, i just get 3 continues beeps after the apple logo loads the files or if i select the cd to boot from. i was able to boot and install windows 7 just fine on the mbp and the hardware all checks out perfectly. am i overlooking something basic here or what? do i need a specific cd other than the snow leopard one i have?