I've got 5, but really only one program running in the background:
*Display Properties adjust
*Speaker program
*Resource Meter
*Volume
*Task Scheduler
Oh, and the time.
The funniest case of too much running in the background was my brother. He's CEO and founder of a very large and successful computer peripheral and networking corporation, but has lost touch with his geek side and has his IT guys set up his laptops for him. We were looking at videos of his kid's model rockets and he was complaining about how his brand new IBM laptop (he gets one every year or less) seemed so slow and was always getting out of resource errors... then he pulled up the task bar to do something and he had about 40 icons in his systray. I explained to him about system resources, memory and the systray and we went about disabling most of the worthless crap running in the background.
As we did this, his 13 year old son was watching. He just shook his head and said, "wow, I can't believe uncle **** knows more about computers than Dad!" I fell over laughing.