I am writing a native code in C to launch internet explorer and then disable task switching (alt+tab, windows key and alt+f4 are disabled). Also, the browser's z-order is set to the maximum so that it always remains on top by using SetWindowPos() api call in Windows api. The code works perfect on XP but on Vista and 7, the only the task switching is disabled (alt_tab, windows key , alt_f4) but the browsers z-order is not set to max. I am able to bring other windows on top of the browser after I click ctrl_alt_del to open the task manager. This works fine in XP but not in windows 7 and vista.

Any thoughts on why this is happening?