In Win XP, sometimes I make settings for which icons should be always shown, and which always hidden, in the taskbar. But sometimes something happens and I lose that. I'd like a program to set them how I want, with a click. So I tell it once, and if Windows XP loses the settings, I can put them back.
PS Tray Factory does it. It has a free trial , is not freeware, but is only $25.
You can backup the system tray setting as a reg file.
Here is an example of what is in the reg file. The data in the reg file is as you can see, specific to the PS Tray Factory program. (So the data there doesn't give away how windows does it). But the program seems to work. It also lets you order the icons the way you want.