Someone asked me if I knew how they could find a window which they'd lost in Windows XP. What happened was that they had been using their laptop in dual screen mode and then went to another location where they only had a single screen. When they ran one particular application it restored its window to the second, now non-existent, screen. Consequently, the window was not visible.
The solution is to move the application back to the visible screen and then remember not to move it to the second screen in the future. This is a bug in the application since 99% of applications check to confirm that they are restoring their windows to valid coordinates before restoring.
What you need to do is this:
1) Press <ALT><TAB> to select the invisible application
2) Press <ALT><SPACE> to select the application's menu
3) Press M to select the Move menu item
4) Use the arrow keys to move the application's window back to the screen where it'll be visible.
The direction which you need to move the application's window depends upon how you set up your secondary screen. Generally the secondary screen is to the right of the primary screen and, in that case, you would simply move the invisible application window to the left using the
Multiple screened computing is very productive, I'd say that two 15" screens are better than a single 21" even though the single 21" has more pixels, if you have any comments please let me know and if you have any other questions which you'd like me to answer for free please send them to Ben Dash at firstname.lastname@example.org