It happens sometime when you are using only few applications for a long time, while other rarely used windows starts taking space on the taskbar. Taskbar Helper facilitates user to organize taskbar by either hiding rarely used windows or moving them to system tray. In addition it shows only those application windows on taskbar which is really needed at the moment.
For Instance, surfing on internet for a long time while ignoring other program windows which are taking space on taskbar.
Uncheck the Visible and check the Show in SysTray Only checkbox and you will find the icon of hidden windows in the system tray. To save settings for the desired windows, go to Preferences.
Now launch programs and windows from the system tray and upon minimizing, you will find them again in the taskbar. To prevent this, check the Hide on Minimize checkbox.
Taskbar Helper Crashed few times while testing on Windows 7. It works smoothly on Microsoft Vista and Windows XP.