Windows 7 missing shared dll

I'm facing some problem with my laptop. I'm running windows 7 home premium 64-bit version. before 3-4 days, my system started showing error messages while trying to open any installed program except those that came with the system. It started showing the message 'dll is corrupted'. I tried scanning for virus using mse and McAfee, but detected nothing.

It also changed the appearance of the application's icon. I formatted my system twice in last two days for same reason, but situation is again same. what according to you, could be the possible reason behind it? please help me to fix the problem