I'm hoping that one of you might have experienced this problem before, and could perhaps give me some advice on how to fix it?!

I have a Gigabyte GA-P35C-DS3R motherboard based system running XP PRO SP2 (latest redistributable).
It doesn't recognize the onboard USB ports or headers as USB 2.0, only USB. My (ALi) PCI USB card runs at USB 2.0 without any problem.
In Device Manager I have 3 Universal Serial Bus Controller entries, each with devices, controllers and hubs listed within them.
From what I can tell, I think that the problem is that there are entries listed as: Intel(R) ICH9 Family USB Universal Host Controller, but no entries listed for an ICH9 Family USB Enhanced Host Controller...

So far I've tried:
re-installing XP SP2, installing the latest Intel drivers, (Award) BIOS etc., enabling USB keyboard/mouse in the BIOS, disabling the serial and parallel ports (to try and free up resources), uninstalling the Root Hubs (XP normal mode) and cursing it profusely... none of which has worked.

I read somewhere that I might have to disable ACPI, but it doesn't appear to be an option in the BIOS.

Can someone help? I'm out of ideas

Have you installed the Intel chipset driver? If yes, you can delete the troublesome devices in dev mgr and restart pc.

You can also clear cmos & load defaults in bios. It should work that way.