Installing a USB-2 card

[R. P.]

When I attempted to install a 5-port USB-2 card in my PC having two
built-in USB-1 ports, the new card did not override the USB-1 controller
and its IRQ. Instead it left it there and was trying to grab 3 separate
IRQs for itself (actually, 2 of those 3 IRQs were the same.)
My PC did not like this and no amount of card swapping could give me a
workable IRQ sharing situation. My OS is XP Home Ed.

When my office PC focal guy installed another (a different) 5-port USB-2
card into my work PC, it resulted in the old USB-1 (or USB-1.1) disabled
and its IRQ reused by the new USB-2 card. I like this and so does my
work PC. My office OS is Win2000.

Can anybody explain why such different outcomes and just how it is
supposed to work when one installs a USB-2 card? Anybody here with
similar experiences?

I am also curious about those USB-2/Firewire combo cards and how they
handle the IRQs each may be needing. Do they share the same one (by
assuming that only one of them works at a time,) or they need separate
IRQs for USB-2 and the Firewire controller?

Thanks,
Rudy