Couple things come to mind:
1) Check the settings for the monitor (buttons on front) Appears the trapezoid settings might be off.
2) New drivers
for graphics adapter (go to graphics adapter manufacturer's site and grab latest driver
3) New drivers for monitor (same as adapter)
1. I don't think its monitor problem, it appear after a long time of usage (day base), and if i maximize the application it's ok.
2&3. I'll try this but last time I remember update all driver and Windows 7 itself ,still appear.
Ted's advice is good, but I've posted this link in the hope it may point you in the right direction.
You may experience display corruption issues on certain Intel graphics processing unit (GPU) chipsets in Windows 7
This may help too.
Distorted or skewed image on monitor.
I'll try this