I had a clean install of Windows 7, all drivers working, no hardware or software conflicts. I also have a clean install of windows XP on another partition with no conflicts. On either system the boot-up is problem free and there are no errors at all, the OS loads just fine, but, the left-click button on my mouse won't activate or open anything. Moving the mouse over the START button on Windows 7 won't make the start button "shine" like it does and I can't open any of my system tray items, that is, until I hit ctrl-alt-del and then my mouse starts working perfectly. I close the task manager and the mouse continues to work fine. So my temp fix upon starting either version of windows is to hit ctrl-alt-del the one time and the mouse works. I can live with it but I would like to find out what is causing it.