HP Pavillion zd7000 with a 3.4GHz P4HT, 2GB RAM, 120GB 7200RPM HDD, nVidia GeForce 5700, DVD-RAM burner and a 17" 1680x1050 glossy LCD display. It weighed eight pounds on it's own, plus two pounds for the AC adapter and another five for the two extra batteries (since each one only lasted under 90 minutes playing DVDs, I needed three for a cross-country flight). I flew a great deal and it was murder on my shoulder hauling it around.
Oddly enough, as soon as I bought my Mk. I MacBook (2.0GHz Core Duo the day they were first launched), I stopped flying. Still, never regretted buying it and it served me well until I replaced it with a 15" MBP last month.