Just ordered the low end version for college but opted to upgrade the hard drive. I'm currently on a Sony Vaio Pentium 4, 2.4 ghz machine with 1.5 gbs of ram. How big of a performance boost will I see? This is my first Mac, I'm a little scared to be venturing into new territory right before I head off to college. Any advice from some experienced Mac owners? What are your recommendations for programs to download? Thanks.