Do Hand-Me-Down Computers Help the Environment?

I just got through cleaning up and prepping my old 12" G4 Powerbook (quite seriously, the best computer I have ever used), to give to a friend whose 1st generation iBook is starting to wheeze with the things she needs it to do (and who is giving it to her Mom whose computing needs are relatively modest in comparison).

Now, as a preamble, I try to live quite greenly. I use low power appliances wherever I can, use public transport, take the train whenever practical instead of flying and in general, think of myself as a (compared to most people I know) as quite an easy-on-the-planet kind of guy. My problem is computers. I know they are horrendously toxic and everything about them from manufacturing to disposal is the anti-thesis of green but I make both my living off manipulating and making them more effective.

In my mind, the hand-me-downs kinda offsets the fact I generally pick up a new laptop about every 2 years since the actual life of my computers is much much longer and prevents new ones being purchased or bought by those people (in fact, my brother is using a six or seven year old Sony Z600Tek that I used as my linux laptop for ages. In fact, having me switch back to Linux from my mac would probably obviate my need to get new machines quite so often to even be better than that).

Is it true though? Does this count as moderating consumption or am I just doing a feel-good exercise that makes me feel like an altruist and an environmentalist when I’m just trying to assuage white, worried and well-off guilt?