Suz, if your easy child I'm assuming you're running Windows XP. XP is made to boot with nothing running in startup (I dont know about Vista because I dont like Vista and am avoiding it like the plague).
To access the Startup menu in XP, Click on the Start button, click on Run and type in: msconfig and press enter. Then click on the Startup tab.
You can deselect anything you dont want to run on startup...everything if you want to. (I leave my firewall and antivirus in startup, but that's it.) Click Apply and then reboot (cause all those programs that run on startup are still running in the background slowing your computer down).
When you reboot, you'll get a message saying you've made some changes, blah, blah, blah. Just click the box next to 'don't show me this again' and click OK.
20 minutes is a really long time, though. Sounds like you have other maintenance to do on the computer, too. I would clean up temporary internet files and run defrag, too.