Prevent Steam from Running on Startup

If you have Steam installed on your computer, then it defaults to running whenever windows is started (usually it spends several seconds updating).
If you want to stop this from happening:

• Open the Steam menu and click on Settings
• A Settings window will appear:
  • Select Interface on the left
  • Untick Run Steam when my computer starts
  • Press the OK button

Note that after doing this you will still be able to run Steam from the start menu (and Steam will run automatically when a game is started)