So my macbook has been running pretty slow for awhile now, I'm assuming because I have 20 GB left of my 160GB hard drive. I'd like to upgrade the hard drive, but how do I know specifically which one to buy? macconnection.com seems to have loads of different brands and to be honest I don't know what any of the specs mean. I think I'd like a 500GB drive. I'd also like to upgrade the memory from 2 GB to 4 GB. Any help would be insanely appreciated.