Especially if you have noticed a slow down in system performance and you already defrag the hard drive.

The processes running on your pc at any moment in time can be

• genuine system process
• A un-necessary process you don't require
• A Trojan horse masquerading as genuine system process

Unnecessary process and Trojans can take up valuable system resources up and slow down your pc.

In Windows Xp pressing Ctrl + Alt + Del  once will bring up the task manager window , from here click on processes tab .This will show a list of processes currently running and there memory usage . You can stop any process that is not required.

The only problem is the file names are given and you need to identify what each process is.