Well, I have a hitachi hd in this custom built desktop of mine and love the thing. Its quiet - I can't hear it at all. My seagate in my single core athlon makes some sounds when reading/writing, which can actually get annoying. I replaced the stock fan in that old athlon since it didn't need that much cooling, and threw in a huge heatsync with big finns and a small case fan that runs at low rpm's. So far, everythings working smoothly with bearly any noise, which was my goal since the computer could get a bit loud since it was right next to my room. Mind you, I have this custom built one in my room with me but I can only hear that if the CPU is under load.

My dream system though would be water cooled. I hear they're so quiet you can hear the hard drive - on most computers that's bearly possible unless you use an hd inclosure. Anyway.

Yeah, high performance works too. I love this so much more than the acer though. The acer's 3 cell battery got an hour and 45 minutes at best - and that was pushing it. With skype on, my asus averages around 4 hours. Acer managed about 45 minutes. My asus has the 4 cell battery - acer had the 3 cell.
I had some fun things to worry about with the acer too, like jaws randomly unregistering itself and my video intercept (jaws cursor and what not reading things) stopped working.
I love the internal microphone on this though. Noise suppression is seriously neat - if you have something humming in the background, it cutts it right out - it made my moms vacume sound tinny and, what's that word, unnoticeable compared with the setting disabled.