I hav a gigabyte G31 ES2L, but will Nvidia GT220 wrk on it, its pci-e 2.0 & my m/b is PCI 16x?

Yes, it will work. It just won't work as well as it could. PCIe 2.0 is twice as fast as PCIe x16.



In the following, PCIe x16 is "retro-named", so to speak, as PCIe 1.x:



http://en.wikipedia.org/wiki/PCI_Express