Go to Start; Run and type in msconfig. Hit return. When the dialogue box comes up choose the startup tab and that will show you all the processes running at start up.
Now go to click here
Scroll down the page to the Search function. You can search for the various processes you have running.
The results will tell you whether they MUST be running, can be stopped from running, definitely shouldn't be running (probably a nasty) or left running only if you deem it necessary.