KWheezy is not for old equipment, or less than 1.5GB ram, realistically, unless you strip packages out of it, but that defeats the purpose. It still, fully featured, idles at around 600MB ram compared to a similarly feature rich Windows 7 which idles around 1.3GB ram, so it is very light by comparison.
Lubuntu or similar is the way to go for old (former XP) machines, a friend of mine has an old netbook, 512 ram, Lubuntu boots to desktop on it in 7 seconds.
For me, personally, KWheezy has ended my distro hopping, and the need to ever use Windows again (at home), so goodbye Micro$oft, game over.
Other Linux distros could easily be built up to a similar level of included packages and functionality (see how much that would cost with Windows, done legally), but KWheezy does this out of the box, so why bother