I havent gone out and bought new systems.. i bought one back in '99. (Generic Cyrex 333Mhz piece of junk) and whenever something broke, I upgraded it. By the time I finished paying for it, the only original piece left was the floppy drive and maybe a few screws.
333Mhz cyrex to 800MHz Athlon Slot A to an Athlon 1600 now.
It's on it's 5th board, 3rd case, 2nd monitor, 3rd processor, 6th keyboard, 2nd CDRom, 4th harddrive.. 3 power supplies... in 5 years.
It was kinda funny, I spent about the same amount on my computer as I spent on my car at the time... once I got rid of the car, the computer stopped breaking.