I think it depends on what programs you have on your computer, and how many of them tend to run some part in the background.
I have my computer set up with mobile racks cause I'm not the only one that uses this computer, and I don't exactly want my hard drive to crash from something I didn't do. Also it makes getting back in action easier from a hard drive crash should it ever happen.
On the hard drive I'm on, which I have hardly anything instlalled, I have 33 processes running. On another, which I have most of my data and programs located on, I usually range around 45. My mom's hard drive I think has 50 or more, and she rarely ever uses it, but has installed a number of programs.
Have you done a virus check and spyware scan? Do you know which programs run most of the time that don't need to, like Quicktime or Real Player, or Windows Messenger, AIM?
I believe you can change starup options by going to Start, Run, and typing in MSCONFIG and click on the Startup tab. But be very careful. You really gotta know your computer inside and out before you start messing with anything in this manner.
If you already know all this, then forget everything I said and smack me with a brick.
I'm sure others with more comp service experience can help you out more than I can.