Spyware Elimination

My computer is my domain. I want to know what goes on here. Microsoft provides some sort of list with the "Windows Task Manager", but it is wanting. In particular, the svchost listings are practically useless, since there are so many of them and they are non-specific.

How can I know if a process or thread running in my machine is something I do want to be running ?

The Task Manager window should be the primary control on the activities in the PC, and the primary way to end malfeasance, malware and viruses.