I decided to add progress bar to the Windows 7 Taskbar in my Timer app.

I started by downloading and compiling the Windows API Code Pack in Release mode. I then added a reference to the Microsoft.WindowsAPICodePack.dll and Microsoft.WindowsAPICodePack.Shell.dll files to the project. After that add the lines:

using Microsoft.WindowsAPICodePack.Taskbar;

to your using statements. When the clock starts running I create the progress bar in the taskbar with:

// Initialize progress bar
if(TaskbarManager.IsPlatformSupported)
{
	TaskbarManager.Instance.SetProgressState(TaskbarProgressBarState.Normal);
	TaskbarManager.Instance.SetProgressValue(0, (int)this.totalTime.TotalSeconds, this.Handle);
}

to stop the progress bar:

// Stop progress bar
if(TaskbarManager.IsPlatformSupported)
	TaskbarManager.Instance.SetProgressState(TaskbarProgressBarState.NoProgress);

and finally to update the progress bar on each tick:

// Update progress bar
if(TaskbarManager.IsPlatformSupported)
	TaskbarManager.Instance.SetProgressValue((int)this.totalTime.TotalSeconds - (int)this.time.TotalSeconds, (int)this.totalTime.TotalSeconds, this.Handle);