here’s the problem…
I have 3 PCI slots and 1 PCI Express slot.
My graphics card is big and has its own fan. It is in the PCI-E slot and is so big the it blocks 1 other PCI slot.
That leaves me with two slots left. One for my Multiface and one for my wireless card. Both of those slots have USB ports assigned to their IQ also… so I don’t know if switching the two would make any difference…
Without knowing more about the IRQ routing of the 8400’s motherboard (and I don’t know much about PCI Express), I wasn’t sure if it would make any difference, either–just something to try which has made a difference for others.
However, another, simpler thing to try which I just remembered is to use the free dbldawg utility to adjust the PCI latency settings. The idea is basically that each device gets a certain amount of time for its “turn” using the PCI bus before it has to give it up to the next device. Video cards often get 248 ms, while other devices (sound cards) often get much less time, e.g. 32 ms. Bringing the video card down to 32 ms might help–it made a difference for me.
The dbldawg utility changes are lost on reboot. The site has a $10 utility that will restore the changes on boot up. Also, if the changes affect your gaming, I suppose you may want to set the video card back to 248 ms (haven’t tested this).
dlbdawg can be downloaded at the bottom of the page here.
HTH
Tony
EDIT: woops – double post – ignore 
Big changes arent always needed with PCI latency though. The vid card could probably be dropped down to 96 or 128 without much gaming performance loss, but check if there’s a sata raid controller onboard too, as they’ve been found to be a culprit in the past - lower it’s latency, and bring up the RME a notch or two.
Willy.
You might even want to try disabling the WiFi network card in the Device Manager during times that you are doing DAW work.