A: I can only give a 
pointer to source code. Take a look at
 4067 Jul 1 1993 ftp://garbo.uwasa.fi/pc/turbopa7/cadthf10.zip
 cadthf10.zip CadThief TP6+ unit for trapping ctrl+alt+del, 
M.Hanninen
and
 30673 Oct 13 1987 ftp://garbo.uwasa.fi/pc/turbopas/keyint.zip
 keyint.zip Disable alt-ctrl-del + other int09h TP tricks, N.Rubenking
and
 7105 Apr 19 10:51 ftp://garbo.uwasa.fi/pc/turbopa7/cad_int9.zip
 cad_int9.zip Disable Ctrl-Alt-Del via new TP kb interrupt, 
J.Robertson
   I have utilized alt-ctrl-del disabling at least in one of my own
programs (PESTIKID.EXE). The code is not available, but the 
general
idea is replacing the old keyboard interrupt ($09) with a handler of
one's own. If the handler detects alt-ctrl-del, the keyboard is
reset, else the handler is chained back to the original interrupt.
The chaining requires a rather complicated inline procedure 
provided
in TurboPower Software's kit. An additional complication is that the
del keypress must be intercepted already at the relevant port $60,
and the alt and ctrl status must be tested, so that the rebooting
will not be invoked. Resetting the keyboard requires accessing 
the
$20 and $61 ports.