Technically, at a fresh startup with nothing running and no windows open, nothing should be there.
But you should have anti-virus, various drivers, firewall, etc. that will load at startup, as well as some Windows components.
First thing you should do is go open the Windows Task Manager (ctrl+alt+delete) and look up all of the processes there at
http://www.processlibrary.com/ so that you know what they all are. That way you can better judge whether or not you need them at startup.
Then you can go to Start -> Run... and type "msconfig". Under the "Startup" tab, you can select which processes you want loaded at startup.
Oh, and if you aren't sure about something, feel free to ask.