Shrinked monitor of a personal computer

i have exprienced this problem, my monitor shrinked vertically, it also flickers, i normally play on line games, does it affect my monitor in everyday playing? i already have tried every possible solution i have, setting my hardware acceleration, and everything about my computer display, but nothing happens. any body can help me solve this problem of mine. i hve tried to change my AVR, thought that i am just experiencing power loss, i also did change my connector from monitor to CPU/AVR.