I started up an old PC which I suppose was set up with dual monitors. After the Windows XP loading screen, I just got a black screen. If I move the mouse to the left the pointer appears on screen. I think the Windows login dialog is appearing on the phantom second monitor, because I can't right click on the desktop and the Ctl+Space then M trick doesn't work. If I plug the monitor into the second VGA out I get a 'Signal out of range' error on the monitor. How do I get around this? It seems so stupid.
I believe you can change the resolution in safe mode. Hook your monitor up to the one that says "out of range" and then start your computer up. Repeatedly press or hold down the F8 key while the system is starting up. You should get an option to go into safe mode. It should load windows in low resolution. From there, try changing the resolution and dual monitor settings and then reboot.