The correct answer to you question is rather hard to find. But i found it.
I self had this big icon issue in my quicklaunch bar. After trying your tip with xp style and classic style the icons remained big.
The trick is when you have your taskbar locked you can't change all the hidden stuff
Uncheck lock taskbar and rightclick in empty space somewhere in the quicklaunch area. When done correctly you will see some extra options and menu to change size and textlabels.
Is this worth an easter egg?
