http://www.nikonchat.com/nikkor-18-200-lense/

lens would be best for me Nikkor 18-200 or Tamron 18-200?
I have a Nikon D40 and would like to buy a zoom lens for me. as d40 does not support I go to VR Nikon 18-200 or Tamron 18-200 .. The reason is that this is a huge price in India …
wait a sec … Nikon, the lens has VR. So the D40 will work with the VR lens. I have one and it works. The D40 is not compatible with the Tamron lens unless it has a built-in autofocus motor, which I do not think so. Sigma has HSM lenses autofocus with the D40 to check those out too. Why not buy the 55-200 VR because you already have the 18-55 that came with it.
Nikon DSLR + (sigma 10-20+Tamron 18-200+Nikkor 18-55)