A variety of programs are running on your computer at any time. Even if you don't have programs such as Internet Explorer, Firefox, Word or other applications running, programs run in the background. Windows includes a tool called Task Manager to let you see the programs running on your system. Task Manager shows programs running in the foreground, which are visible to you, and programs running in the background.
Right-click the Taskbar. Click the "Task Manager" option.
View the applications running in the foreground using the "Applications" tab. If any of them is frozen you can click on it and click the "End Task" button to forcibly close it.
Click the "Processes" tab to view all the processes currently running on your system, including background programs. The "End Process" button works to close processes in the background. Be careful not to close important background processes.
Some viruses and other malicious programs are capable of masking themselves, making them difficult or impossible to spot in Task Manager.