looks like it's a Intel G45 chipset - so 16gb should work, however you need to be careful when selecting memory - there might be max size on the chips on memory

looks like it's a Intel G45 chipset - so 16gb should work, however you need to be careful when selecting memory - there might be max size on the chips on memory module (so there are memory modules with 8gb with 8x1gb chips or some with 2x2gb etc.pp. - we had some trouble updating older dells with the newer modules with less chips. It's called low density I think.