1. Move mouse in the header between columns 2. Press left mouse button 3. Move mouse 1 pixel right You'll see, that the adjusted column streches as far right as possible. The next mouse move returns the column to the mouse position.
Confirming it in win98, build 2001081703. Marking as New.
-> XPToolkit: Trees
Ouch, it was the wrong component! Now I've found a proper dupe: bug 79961 Sorry for the spam *** This bug has been marked as a duplicate of 79961 ***