On the low-spec end of the scale, I think Windows XP is useful on eveything above 1 GHz. Still, running it on a 400 MHz Celeron is worth a try, but that machine would perform better with Windows 98. Maybe someone who finds a trashy machine from the year 2000 wonders about it.
My favourite piece of software is Teamspeak 2, the old voicechat client. It runs on newer Windows systems as well as on older Windows systems, like XP. Still, lots of open public servers available.
Aren't there any proper XP cracking tools out there? Just asking, because they exist for other Windows systems as well.
Good guide, prints. The amount of current Windows XP videos, that miss out on the so important new browsers like New Moon for example, still show us that it has to be written down, how XP can be done properly nowadays.