Is this one of the old black-bezel "PanelView 1000 Standard" or one of the newer Windows CE-based, grey-bezel "PanelView Plus 1000" terminal ? Or even a PV1000e "Enhanced" terminal from the early Nineties ? The part number sticker will tell you for sure; 2711, 2711E, 2711P are the Standard, Enhanced, and Plus terminal bulletin numbers.
Displaying half a screen certainly isn't standard behavior... my immediate guess is that the video section has been damaged.
The keypad terminals generally have a key sequence to go to the Configuration screen, like leftarrow/rightarrow or Ctrl-Alt-Enter. It depends on which model and which firmware revision you have. The touchscreen terminals generally need to be rebooted and they'll show a white box in the lower left corner that you touch during bootup so that the runtime goes to the Configuration screen.
The primary thing you need to do is recover that user program. Using the transfer utility (again, different ones for different Standard / Enhanced/ Plus terminals is the easiest method, though there may be CompactFlash or even USB options.