Generally speaking, it is best to disable the program through its own setup options or preferences. Consult the software documentation or explore its setup options and preferences for options to "load during startup", "show icon in system tray", or "run in the background".
As a secondary option, you can manually disable programs that load during startup using Microsoft's System Configuration Utility. To open the System Configuration Utility:
Click "start" and then "run".
Type in "msconfig" and then click "ok".
Select the "startup" tab.
Entries in the startup tab's list are various programs and other functions that load each time you boot your system. Uncheck the box for an item you do not want to load during bootup.