I used Ultimate Windows Tweaker and disabled Aero Peek, again i enabled it, though there was no good result. Click Start, type aero in the Start Search box, and then click Find and fix problems with transparency and other visual effects.
Windows Aero features in Windows 7 has been greatly enhanced and improved with new features such as Aero Peek.Without Windows Aero Glass Transparency effect, the many premium user interface (UI) goodies and extravaganza visual experience such as windows with translucent glass design and new windows colors in Windows 7 won’t be enjoyed by the system users.