The timer/ESC idea will kill resources and probably produce all kinds of other issues as well.
You are talking about catching/preventing a seriously high level API call. You can do some web searching and you might be able to find something. I did that and found a bunch of solutions but I really don't know any that work and have never tested any myself. I just know that the ctrl+alt+del combo is a high level code call.
I tend to agree with jebenson and SiriusBlackOp. This functionality would best be controlled by Windows. If that is not an option (maybe you are doing this on a home pc or such where there is not domain), my next bet would be to look for a third party program to do this for me. As Sirius said...you run the risk of locking yourself out of your own PC/causing some other Windows functionality you DO NEED not to work/etc.
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People think it must be fun to be a super genius, but they don't realize how hard it is to put up with all the idiots in the world. (Calvin from Calvin And Hobbs)
Robert L. Johnson III
CCNA, CCDA, MCSA, CNA, Net+, A+, CHDP
VB/Access Programmer