P3 is good enough, I run it even on a P2, only RAM shouldn´t be too small (384mb here, works fine, only graphical installer isn´t working because it demands 400mb at least

)
I use a Linux box for it, but I´m pretty sure it´s no problem to integrate Solaris in an multi-OS environment with XP too. all you need is about 10GB space (standard install is 7.6GB, it´s that big because it allocates free space to the services).
check your PMs...
