Sorry I found this article that helped me resolve at least this problem
It's the F problem!!! (Function Key)
Read on to fix it..
Had the same problem with adding a monitor to my xps.
1.) Attach the connector lead of the monitor to your laptop
2.) So you don't see the display?
3.) The laptop has an Function key (Fn key next to the windows start key) on the keyboard. Press and hold the key, and hit the F5 or F8 key or that F key which has the monitor icon on it (it is F5 on toshiba and F8 on dell).
4.) This should fix it.
5.) Sometimes a high resolution to an extended screen can also be a cause of non-display. Just reduce the resolution of your new (additional) monitor to 800X600 and that must fix it.
6.) If these two still don't fix, then your next bet is re-installing your display device drivers. "