Agree completely with what's been said about Linux/LAMP. I bought an old, old Dell D420 (2006) laptop for a demonstration earlier this year of what you could do with older hardware and a LAMP stack. I have 1GB RAM, a 60GB HDD, and a puny 800Mhz processor...and I'm churning along in Drupal quite decently.
I recently moved off-grid and I am unexpectedly having to rely on this laptop (less energy usage than my big dual-core desktop) ... but it works just fine. (Side benefit to Linux development: it's just a heck of a lot more fun than Windows! You're back in charge of your own machine - and that's a good feeling...) Chana
