Explorer.exe using 50+% of CPU

Few days ago I noticed my CPU usage is very high, I tried rebooting few times and nothing changed. When I go to Windows Task Manager/processes I see my explorer.exe file is using more than 50% of my CPU even when no app was started...
I tried everything I know. Scanning PC with Antivirus, doing system restore etc.
Does anyone have any suggestion?

Also, here is my configuration:
MSI GE620 DX
CPU: Intel i5 2430M
GPU: NVIDIA GT 555M / 2GB DDR3
RAM: DDR3 4GB
64-bit Windows 7