Assuming it's your computer...
control panel > administrative tools > services
There's a lot of programs with an automatic start up that can be changed to manual or even disabled. You just have to be careful. Do one or two items every few days and make a list. If it's a new computer, make sure you strip all the bullshit programs off that manufactures put on. If you're pretty good with your computer, disable all of the automatic update programs, then do them manually once a month.
Some garbage from services might include:
Clipbook
Mesenger
Network DDE (2)
Task scheduler
Wireless blah blah
Windows Time