"z buffer"(depth buffer?) does not appear to work as described in an XNA tutorial

[Tom]

@jetbuster

GraphicsDevice.DepthStencilState.DepthBufferEnable = true;
GraphicsDevice.DepthStencilState.DepthBufferWriteEnable = true;

That isn’t the correct way to do that and will get you into trouble. Instead just do this:

GraphicsDevice.DepthStencilState = DepthStencilState.Default;

That is the correct way to do what you want.