Try the following method (From the Custom Taskbar Thread here):
When replacing a specific dll file in windows use the following technique (Using the HTCVolumeControl.dll as an example):
· Open Total Commander and go into /windows rename current HTCVolumeControl.dll to HTCVolumeControl.dll.bak
· use TC to move the new .dll file into /windows
· soft reset.
· You may now delete the .bak one.