Programs are not the only items which run in XP/Windows...there's another category of items called Processes.
A process may be either a Windows function executing...or it can be related to software which you have installed. An example of such will be the scanning function of your AV, the update function of various programs, etc.
If you want to investigate processes running, you need to look at the individual programs/functions behind each listed process. Google can assist in this.
It's not uncommon for multiple instances of svchost.exe to be running as a process. To investigate what programs may be running such...you can use the following link for direction.
How to determine what services are running under a SVCHOST.EXE process - http://www.bleepingcomputer.com/tutorials/list-services-running-under-svchost.exe-process/
What is the System Idle Process - http://ask-leo.com/what_is_the_system_idle...of_the_cpu.html
Task List Programs - AnswersThatWork's famous Database of Processes, Startups & Services - http://www.answersthatwork.com/Tasklist_pages/tasklist_n.htm
TaskList.org - List of Windows Proccesses and Descriptions - http://www.tasklist.org/
Windows Process And Task List - http://www.neuber.com/taskmanager/process/index.html