These are the supported configurations (according to Intel)

DisplayPort + DisplayPort + HDMI* or DVI or VGA or DisplayPort or Built-in Display2

DisplayPort or HDMI or DVI or VGA + DisplayPort or HDMI or DVI or VGA + Built-in Display

DisplayPort or HDMI or DVI or VGA or Built-in Display + DisplayPort or HDMI or DVI or VGA + Intel® Wireless Display (Intel® WiDi)

Note that the built in display in addition to three external monitors is NOT a supported configuration - you can have a max of three displays INCLUDING the internal one.

www.intel.com/.../000005556.html

Thanks for the reply.  As mentioned I've done the

DisplayPort + DisplayPort + VGA set up

I'm not using my internal screen

No matter which combination I use I can't get three monitors working.