I know you said you removed the 2nd monitor from the Nvidia control panel, but did you also go into Windows' Display Properties > Settings, to ensure Windows doesn't still think you have two monitors?
I'm not convinced that would be the answer, especially as you have tried connecting another 2nd monitor, but it s worth a try.
If that doesn't work, try this.
With the application icon showing on the Taskbar, right click that icon and select Move. Without moving the mouse, click and hold down the left mouse button. (If you move the mouse before holding the click, you have to start again). Now, drag to the left. Selecting Move should fix the mouse cursor on the application header bar, so left click, hold, and dragging should move the application back into view.
If the Move option is grayed out, select the Restore option. Tha should reduce the hidden window from Maximized to normal size.
If that works, then just minimize the window, restore it, and it should now be fixed on the primary monitor.
Hope that helps.
For about 5 months i had two monitors installed and they were working fine. i decided i needed the extra cash so i disconnect my second monitor after removing it from my nvidia control panel. now when i open some programs they only show on my taskbar but not on my main monitor. i have connected another monitor with the same settings and it doesnt open on that monitor either... i have no clue to fix it and have tried unistalling my video card drivers from hardware manager. i have tried unistalling the programs and re installing and i even went into bios to see if they were opening on onboard invisible monitor but there was no setting for that in my bios. please help any suggestions would be great