smoochie is correct, I am currently running a 2.0 card in a regular pcie slot & it works fine
. What I meant was Yes, and without any speed loss, because as of right now, no cards use more than the PCIe x 16 1.0 bandiwdth anyways. My bad skeletor!
A PCI-E2.0 will work perfectly fine in a PCI-E, as
unless you're running two copies of Crysis on the same computer.
Yes you can do that. They are compatable. If you put a 2.0 card into a 16 slot it will only run at 16x speeds not 2.0 speeds. This is similar to running a pci-e 16x card in a pcie-e 8x slot.. and if your can put a 16x card into a 2.0 slot and it will run normal.
Close, but no. Your card won't run slower in a PCIe 1.1 slot if it's PCIe 2.0. We haven't maxed out the bandwidth of 1.1 x16 yet. Sure, we're close, but we're not at that limit yet. The only card that could come close to the limit we have is the GTX295.
x16 is not a speed. x16 is the amount of lanes it has to work with. PCIe 1.1 and PCIe 2.0 have the exact same amount of lanes, the only difference is that 2.0 has double the amount of bandwidth per lane.
PCIe 2.0 is just to give us buffer room to work with, PCIe 1.1 will work fine with any 2.0 card you can throw at it.
~Gooda~

I'm Using a 8800 pci express 2.0 on my pci express 16x worked fine there backward compatible.
