Type system configuration or msconfig in the Windows Start menu box, and click enter then go to the startup tab, and uncheck programs which you don't want to Startup when Windows start. Lastly click the Apply, or OK button on System configuration.
You can also start the run programs from the startmenu, and type in MSconfig to open system configuration if you use Windows XP or older.
This also make your computer less slow when you are using it after Windows started, and there would be fewer notifications and pop-up while using your computer.
A lot of people consider the loading time after Windows booted to also be part of the boot/start up time. I notice some heavier apps like Antivirus, and Antispyware software can make the computer login to Windows many seconds slower, or make Windows slow down while the Antivirus is loading and running in the background like older versions of Norton. I seen PCs which took many minutes to boot, but I got a feeling they were heavily infected with viruses or the hard drive was not disk defrag in many years.
I mainly just disable all my instant messengers, and start up apps I don't use often since I like keeping my system tray clean, and don't like those notification which pop-up in the system tray or desktop from bothering me when I first turn on my PC.
