those ram slots are in no way prehistoric. They're the current standard. If you hooked ram up via PCI slot, you'd have some really slow, fairly worthless ram. It might actually slow a semi-new computer down a little.
Ok, obviously you are new to these forums. Name calling will not be permitted or tolerated, especially when you come on these forums to ask for help or for opinions, then when we offer our two cents, you cut us down and tell us were wrong...when in reality it's you who is wrong.
So I will ask you one more time, who is the manufacturs your motherboard and what is the model?
The only way that you would have PCI RAM is something old, really old. That isn't even close to todays standards and needs to be thrown away because it's completly worthless.