Can you help me? My Pc is working slowly.

Hi,
I am using Dual-Core (2.60GHz) CPU with 2 GB ram. But it is working slowly. I have not any antivirus and no internet connection. I use a pen-drive to store external data. I installed only 5 to 6 programs including drivers, Video player and Ccleaner. Actually I use my PC for playing games.
