Read other letters about this article
5 year plan, buy $1000, assume it is worthless in the end (recycle or donate):
$1000
5 year plan--buy for $1000 every year, sell for $400
Year 1: $1000
Year 2: $1000 - $400
Year 3: $1000 - $400
Year 4: $1000 - $400
Year 5: $1000 - $400
= $3400
One could also factor in the opportunity cost of not investing the money you could have saved every year by not buying a new computer every year.
I don't think it matters what you buy--just don't buy a new one every year. It will cost you more is bad for the environment.
I won't go into tips on how to make a computer last-there are lots out there--you shouldn't see any major performance degradation over 5 years if you are smart.