I have one AGP slot and four PCI. My AGP has the second-biggest board in that box (second only to the motherboard itself). My PCI slots, pre-power-supply-frying, have gon as follows:
PCI 1: 7.1 sound board
PCI 2: Linksys wireless interent
PCI 3: NONE
PCI 4: NONE
After replacing the motherboard, I couldn't get the WiFi to fit in the PCI 2. This was a headache before, as well. Annoyed, I pluggged it into the third PCI. It fit perfectly. Odd thing is, I can plug other things into PCI 2. It works fine. And it looks the same as PCI's 1, 3, and 4. So what's the magic difference?