Has anyone tried this? It looks quite useful. I have used the hardware
profiles method myself in the past, but it was rather tedious. This does
all the tedium for you. I haven't tried it yet.
SparkleXP is an application designed to tweak Windows XP and improve its
performance. It helps freeing up computer resources resulting in a faster
and responsive computer.
This tool creates a second Hardware Profile and a correlative new User to
get a lightweight desktop. You can choose to boot into your regular or
SparkleXP configuration at startup.

Ciao, Dave