Studio XPS 1645

After I reinstall windows 7 on my laptop, I try to install FassAccess Facial Recognize and its ok. Then I install some drivers and update, I dont know since when the FA is not appear at the logon screen. And I tried to reinstall it, it works for the first time after the reboot, and for the second reboot it disappear again. When I install Dell Webcam Central, it appear again then disappear just like when i reinstall it.

I'm thinkin because I change the logon screen background so it block the FA. But I'm not sure because when I change it back to the default it still have the problem.