Just a thought. I recently found out that a lot of the XP Pro problems stem from the permissions granted a user. If the user is not given full control over the situation at hand regardless of what it is, XP will block anything they try to do. to cure this uyou have to go into the registry and find the slot that the firewire card is in, then right click on it and click on permissions. See if your user id is in there for sull control if not add your user , by clickling on add then advanced then find now and scroll doiwn to your user name and machine id, highlight it then click ok, then your nzame will show up in list , click on full control and read only thenonce boxes are checked click ok. Then try it.
You can find the slot by going to local machine, system, enum pci, then go dowwn the list . usuually the description will be on the second level under each slot.l I usually giv the pe4rmission one level higher than the device descripotion.
This worked for me both with my firewire card and my audigy sound card.
Be careful, I only know this from exerimenting . Always back up your registry, etc, because I am far from a professional at this styuff.