|Try downloading one of the "live" Linux distributions, just to see if you get video by booting to that. It might not solve your problem, but it may tell you whether or not it's a hardware problem. If a "live" CD boots up and you have a display, that would just about rule out a hardware problem. (I say just about, because I once had a nVidia card that worked under linux, but not windows, regardless of driver version used.)|
If we can rule out the hardware, it'll make it a little easier to diagnose and/or fix the problem. It might also pay to unplug the external monitor and check the pins in the plug. Sometimes they can get bent over, which would cause the sort of problem you're having.
Check the cable first, then try the Linux "live" CD. Post back afterwards to let us kmow how it went.
Please let us know if you found someone's advice to be helpful.