At the risk of making myself sound slightly less brilliant than I surely must be, I managed to get myself into a right pickle yesterday with my dual monitor setup.
Using Nvidia dual monitor mode Dualview you have your Windows Start bar on one screen with a clear second screen. Like so:
However, I was setting up a new monitor and experimenting with different resolutions and made it so that the display with the Start bar (and all my applications) was being displayed at a resolution my display could not handle.
My second display, the one with nothing on it, was fine. That's okay, I thought. I'll just right-click my visible display, bring up Display properties and put in a usable resolution for my primary display. Unfortunately, right-clicking the Desktop and selecting Properties opens that window on... the same display as your Start bar. Which I couldn't see.
Right-O. I'll try opening the Nvidia Control Panel from the same right-click menu. That's opens on the wrong screen also.
Here's where a deeper knowledge of XP keyboard shortcuts would come in useful. I know that the Window icon produces a menu that includes a Move option. I'll just Google "move windows keyboard shortcut xp". Right. Where's Opera? Oh.
Now I couldn't just turn the machine off and reboot into safe mode because it is an HTPC and was recording something. So I came up with a brilliant plan. I would move my mouse into the blank screen a different distance and at a different height multiple times and try and drag a window back across. Hopefully, it would be the browser or the control panel. After trying this many many times, I twigged that my browser window was maximised and, therefore, not draggable. I un-maximised the browser window (just moved the mouse to the top of the blank screen and double-clicked) and many, many times later, I actually did it! I actually blind-grabbed a window from the blank screen.
Now, it turns out there is a keyboard shortcut for moving a window and it is Alt+Space then M. Alt+Space brings up the window icon menu. So I could then Alt-Tab to the different windows and move them across to the visible display one at a time.
Sadly, this wasn't the end of my woes as I used the Nvidia Control Panel to change the resolution of the blank screen...
...and managed to blank both displays. How? I do not know but that did require a reboot into safe mode.
The thing I do find odd is that I have no idea when I am going to get the confirmation dialog box after changing my display options. (The one that returns the display to its former setting if you don't click Yes.) Sometimes I get it, sometimes I don't and I don't know what the difference is. I really wish it had popped up on this occasion. Fortunately, Windows XP's plethora of keyboard shortcuts really helped out. Alt+Space->M is one I'm going to remember. Until I forget it. Which'll be about 1 day before I need to use it again, I'll wager.