I think the big issue is that some people don't realize that system start ups are being installed. Take Google Chrome for example, great web browser but without asking it installs Google Update when you install, some other examples are Nero Update, Adobe Update, Java Update I think you are starting to see that there is a pattern here. none of these "updates" are required at start up. They will update when the parent program is used if it is required. I myself have never seen Nero update itself...
Other problems are the sneaky little programs that decide it is better to be running from start up rather than wait until you open them, Daemon tools is a prime example,
As Ian has kindly pointed out msconfig/ start ups tab is the best and easiest way to disable these start ups and regain some of the performance you may have lost.
It really doesn't take too many apps to slow down a Windows OS when they are all starting at once.
Thanks Ian for your guide into this, I'm sure it will help out a lot of newbies when it comes speeding up their OS the easy way.
One last thing to any newbies reading, a Google search with the "start up item" name will normally tell you what it is and if it is safe to uncheck from the start up.
Note: Microsoft Windows Operating System is better left checked!