I'm not sure of the machine specs - I know they're not all that exciting since the machines are over 1 year old. Processor is something like 2.4GHz P4, but the machines do have 1GB of memory. After loading everything, I typically have >400MB of physical memory left. I have no qualms about playing MP3s or opening as many IE windows as I want. I even have a bunch of shortcuts on the desktop that open a new IE process for each provisioning system region, switch query window, etc (nothing like one window crashing and taking out every other IE window).
The applications aren't too bad on CPU or memory - many are web-based and many of the local clients are just IE frontends. The trouble ticket system is the most troublesome - it's a VB.NET application
Somehow, I suspect the XP "distribution" I'm running at work isn't quite like you get from a retail installation. It's rock-solid. The only disruptions I experience are when IT decides to do a push at 22:00 and every machine in the building reboots at the same time...