Another source of startup bloat is the number of programs that are automatically loaded during Windows' boot routine. A wide variety of programs will automatically attempt to load during boot up, depending on what you have installed. These range from the critical (antivirus, system utilities, etc.) to the situational (instant messaging clients, social media tools, manufacturer utilities). If your system tray in the task bar is bloated with icons, this is likely to be an effective tweak to shave time off a slow boot.
Go to your Start menu, type 'msconfig,' and take a look at the Startup tab. What you see is a checklist of all the programs that are set to load automatically during your boot. Some (like your antivirus of choice) are critical and do need to go online right at the beginning, while others (such as messaging tools like Skype) can be dropped from your boot routine to lighten the load on your system and speed up boot times. Please make sure to read up on each item so you're absolutely sure of what they do before disabling them.
Impact: Variable. Depending on how many programs you have loaded, you can save a few seconds or whole minutes if you have a bloated setup.