On my home machines (Home Premium x64 + good graphics hardware; Professional x86 + poor graphics hardware), active taskbar icons apply a visual effect based on the position of the mouse cursor. Transparencies are not enabled on the machine with poor graphics hardware so presumably it's also supported in software.
On my work machine (Professional x64 + good graphics hardware), however, the effect doesn't show. All other effects (glass, window previews, etc) are enabled so it's not a performance problem.
Any ideas on how to enable it, or why it would be disabled?
(It may sound petty, but I'm more interested in how it ended up configured this way.)