you can not change a irq on 2k/xp...if you do it in the bios you will trash xp.
XP and 2k handle the irq assignments very differently then the 9x systems. you could change the irqs on 95,98,and me from windows and fix some odd issues. your problem is probably not irq and more like needing a firmware/driver/bios or a few other system devices needing a driver update.
is your enhanced usb fully installed? sp1 adds usb2 support, check your device manager and see if you have any conflicts next to any usb entry listing...it doesnt always install the enhanced driver...you may have to tell it to look for the drivers. there are a few patches for your machine and a bios update...try them first.
http://h10025.www1.hp.com/ewfrf/wc/s...c c=us&os=228