If you occasionally plug/unplug your notebook from a second monitor, you've likely found some of your windows still on the other screen... and inaccessible. Closing the program can solve the issue, but many programs save their locations and won't return to their defaults, even with a restart. Fortunately, there are a few shortcuts you can employ to get those windows back into view.
In Windows Vista and XP, the easiest way is to right-click on the program in the taskbar and select "Move". Your cursor should change to a four-arrowed one that looks like a wheel wrench. Now you can just hit one of the arrow keys and move your mouse and the window should re-appear on your screen.
In Windows 7, the "Move" option won't be available by right-clicking the icon on the taskbar. Instead, click on the app's icon in the taskbar and make sure it's highlighted. Then, hold down the Windows key and press the left and right arrow keys until the window becomes visible.
Finally, if all else fails, you can right-click on the taskbar and select one of the window organisation options — "Cascade windows", "Show windows stacked" and "Show windows side-by-side". The downside of using these is that they'll resize and reposition all your other windows, which means you'll have to set them back up afterwards.
Bring Misplaced Off-Screen Windows Back to Your Desktop [How To Geek]
Move/Recover Offscreen Window [Microsoft TechNet]