If you go to the display properties page and have another look. It might show 2 screens, if it does, click screen 1 and click on the Identify button (or something like that, I've only one screen here!). If a big 1 pops up on your monitor, we're on the right track. Click on screen 2 and make sure the box labelled "extend my windows desktop onto this display" or something like that is unchecked.
You can move it from the taskbar (or you should be able to), try it with your browser window. If you right-click it and choose Move, the pointer goes to the middle of the title bar at the top of the window, you can then move it around with the arrow keys. You probably won't be able to do this if the window is maximised or minimised. The other major flaw in this plan is that you don't know where the window is, so if it's off to the right and you move the program even further right, it'll be even more lost.
I used to know a method or had a program that would move programs off screen back on, but I don't know where it is now. I'll have a look and tell you if I find something.