Nikon D7000 built in Flash pops with External Flash?

I tried using an external Nikon flash SB-50DX on my D7000. I'm wondering why even with the external flash in the hot shoe, the built in flash still pops up before a picture when auto flash is on?

Is it supposed to do that? Is there a way to turn that off?

This probably happen because you're using the automatic mode "Auto" and the D7000 can't communicate with the flash since it's an old flash, you'll have to put your camera to aperture priority "A", speed priority "S" or manuel "M" setting then adjust the power of the flash manually (if you can, i'm not sure, I think it will be lock on full power). This way your pop up flash shouldn't pop up.

You would be better off with an sb600, sb700, sb800, sb900 those flash are made to work in ttl and use via the Nikon CLS technology but their prices are not the same. Or you could buy old sb24, sb25 + a set of radio trigger and work in full manual.