Im looking at a bunch of different 500GB hard drives to let me run full, or close to full time machine on my MBP. This one is by far the best price for a real brand ive seen thus far. http://www.officemax.com/omax/catalog/sku.jsp?skuId=21168246 I just wasnt sure if it will work on my mac. Will i need to reformat it? and if i do, does that void the warranty?