My PC is taking long time to shutdown from few days and sometimes windows shows error that desktop is not responding and asked me to force shutdown . Please help .

My Computer
- Computer type
- PC/Desktop
- Computer Manufacturer/Model Number
- Self Assembled
- OS
- Windows 7 Ultimate x86 SP1
- Internet Speed
- 4.2 Mbps Up ; 2.6 Mbps Down
- Antivirus
- Kasperskey Internet Security
- Browser
- Google Chrome