I have just had my logic board replaced on my macbook pro 13" (early 2011) after spill damage destroyed the last one. Now it seems i have no operating system on it. When i try to install snow leopard from the disk i got with the macbook it shuts down before the installation is complete. I have wiped my hard drive and performed repairs but still no joy. Do i need to purchase a retail copy of snow leopard or is there something else wrong? Any help would be greatly appreciated. Thanks.