Yes you can put it in a PCI-E x16 slot . If your board supports PCI-E 2.0 and if it doesn't the card will still work but at only PCI-E 1.0. I have a 2.0 card on a 1.0 board and every thing is fine.
The x16 is the bandwidth of the slot compared to a X8 or even a X4.
Like said above it should work just fine. There were only a few PCIe 1.0 boards that had a problem but I think they fixed those with a bios update. They were either Asrock or PCchips I,m pretty sure.