Forcing a resolution on a computer without monitor

I have this computer running an embedded version of Windows 7 and it does not have any monitor attached. It is only accessed with VNC (alternatice for RDP) so a monitor is not needed. The problem is that I really need it to display 1680*1050 and that is possible when I hook up a monitor, but when I take away the monitor it only has a few resolutions left on which it can run. None of them is 1650*1080.

So is there a way to "force" the right resolution? I know there are other questions like this, but they did not have the right answer for me. Switching to RDP is not an option BTW.

I am also quite curious as to why it can only display the right resolution on a monitor. If it is at all possible to give me some insight into this I would appreciate that.

Solution 1:

So this is how I solved my problem: There is this thing called a "Dummy plug". Basically it is just a VGA cable with one of the RGB signal lines connected to GND through a 50-150 Ohm resistor. The computer will then beleive that a monitor is attached, but it can't detect the resolutions it can display so it displays all resolutions.