I fyou like run diags for the video display, you can use MS DX diags for a quick test, did this:
goto start->run->type DXDIAG, then enter, follow prompts

If you have a decent video card, it should provide similar testing, goto its display properties and find the vendors test mode.

However, if the test seem OK, you may a monitor going out or someone touched the LCD too firmly at that area and crushed or distorted the screen in that sport. You swap the monitor to another system and check results for a real quick test.

tada -----Willy Happy