[H] Greg>> P9X79_WS PCI slots too small

[Winterlight]

I need some more USB2 ports so I attempted to install a old Adaptic 
PCI USB2 5 port card in my P9X79_WS. I was surprised that it didn't 
fit in either the white or black slot. So I tried a newer Rosewill 5 
port USB2 card and that didn't fit either. Both are about two wires 
too big for the first slot.. why is that?  I thought all PCI slots 
were backward compatible. So what do I need that will work with these slots.