Bob.........I just did it again and still can't retrieve the darn box.....How do I set the monitor geometry ? I'll try that....Oh ,and I can move my cursor completely out of sight, and when I let go of the mouse, it's gone........imaSIGNr
OK, assuming that you're using the standard upper left pointing arrow for a cursor...
With this cursor the target is the single pixel at its point. This point cannot be moved off of the logical display. Your problem gives every indication of being that your logical display is somewhat larger than the actual viewing area.
The top and the left side should be no problem, if you can move the cursor, out of sight in either of those two directions your monitor's display geometry is totally FUBAR. You shouldn't be able to move any part of the mouse pointer off of the display to the top or to the left.
Now then, bring your mouse down to the bottom of the screen, keep your eyes on the single pixel that is the tip of the mouse pointer. No matter how far down you try to move the mouse you should still see the one black pixel that is its tip. Look hard.
Next move the mouse pointer as far to the right as you can. No matter how far to the right you go you should still see the one pixel wide vertical line that is the left edge of the pointer's arrowhead.
If any of the top, left, right, and bottom conditions described above is not the case then you need to resize your display. The procedure is slightly ro wildly different for every flavor of monitor. If you're in possession of a manual for your monitor, the procedure should be at least outlined there. If not, there should be some buttons, perhaps also some wheels, somewhere on your monitor, usually in the vicinity of the contrast and brightness controls. Perhaps behind a little trap door, perhaps on the bottom of the front bezel, perhaps on the side of the bezel. Maybe little widgets with screwdriver slots. They are there somewhere.
If you're fortunate to have a monitor created by civilized beings, there might even be a button the puts a menu on the screen.
No matter, there will be some sequence of combination of controls that will allow you to size the visible display. Find it and use it to make sure that you can actually see all four edges of your desktop. You want the actual image on the monitor to be slightly smaller than the complete visible area. You want a black margin around the image. It doesn't have to be big, it just has to be there.
Once you properly set up your display, you shouldn't be able to move any object completly off the desktop. If something seems to disappear, look behind your toolbar, you can minimize it or just click on an unoccupied part of it and drag it to the top of the display. If the top of the object absolutely positively isn't there, look real close, then look at the right side of your display. If the left edge of the object isn't there either then you have the equivalent of mice in the washroom. Which is computerese for magic and you'll need the services of a competent metaphysician.