"change the size of thumbnail peviews invista taskbar"

Can anyone tell me why this tweak won't work, i have been trying for a few days now, and basically it shoud work

This is the tweak

Now in the rhs pane, create a new DWORD value and call it "thumbnailsize" right click on it and choose modify, then select decimal option and enter the desired value data in pixels, it can be changed to a value between 32 and 256.

And thats it "simple" well not for me i cannot get this to work

Here is a snapshot

I have windows vista home premium 32 bit