What items do you get when you right-click on the 'jv16 PowerTools 2006' taskbar button?
It should atleast have minimize there.
Also, check try to press alt+space, there should be poping-up an menu now. There should stand minimize also.
If not, it could be that there is some program active on the background which disables this for some strange reason.
I have tested it on my laptop and dekstop computer.
Both are just working fine.