The documentation is a reference that includes way too much information, but I think of special interest to you is this section:
Size of items in taskswitch area of taskbar. One pixel equals 15, again. If you set it somewhere around -300 (experiment, depends on taskbar/captionbar height), you can have only icons displayed there...
I am guilty of providing too much information!
Kellys-Korner is another popular site for download XP tweaks but my problem with so many of them is there is no explanation about anything - it is just download and run (try) this. http://www.kellys-korner-xp.com/xp_tweaks.htm
Look at #97. It says "Undo", but it is really a "Do", so already I have a problem with it.
This is a VB Script (tweak) to download and run that sets the value to -285 which as I mentioned is supposed to just show the icon, but -285 always leaves me at least the first character of text and sometimes a dot or two.
I don't like to just "try things" - I want to know that the devil is going on. What does it do? What if I don't like it?
Could it be that somehow that little script was run on your system in the past?
If I was sitting in front of you computer, I would just take a look at the WindowMetrics part of the registry and see what's up and do something about it if needed - whack it and see what things look like. At least when you get done, you will know more than when you started.
Some folks are not comfortable with the registry, so if that is you, then try to find somebody that is.
Remember - there is no "undo" or "quit without saving" in regedit!