The task manager is good utility to view and end processes in windows xp but where it fails is in enumeration and displaying information about the running system processes like svchost and the services which are running under that.
But windows provides a good command line utility for exploring processes and the sub processes running under it, this utility is called tasklist.

For example: tasklist /SVC will display the services running under a process which it normally won't do.

Note:To get more info about any windows command type command name, give a space append it with /? for example if you want to view the help for directory command type dir /? it will display what we call man page in linux based systems.

Also a good utility to have when you are not sure what processes are running (maybe trojans,viruses) is Process Explorer which displays information about each process, The dlls (dynamic link libraries) that it uses for running, memory image path, etc. This can be downloaded from here