I did it by using visual basic programming....
I kept one ".exe" designed in
vb, in system start up which kills explorer.exe & it runs in full screen mode when system starts.....and when it runs in full mode it disables "window+D" .
but by pressing "alt+contrl+del" task manager can be accessed OR by pressing left shift key all system startup programs can be bypassed when system starts.......
I did research on boot startup......but not found solution...
try to get the source code of CYBER CAFE MANAGEMENT softwares
they are using the same thing when client program runs at system start up.....
try 4shred.com & esnips.com.....