To do this you would use the Windows DDK, WinDbg, and VC 6.0 to write a MSGINA.DLL, which would be called during an attempt to invoke the SAS (secure attention sequence, also known as Ctrl+Alt+Del).
Developing such a DLL is very difficult, because if you make any mistakes you end up with an unbootable PC. Perhaps you could find a vendor selling the source code for one, otherwise it will require a person with specialized skills to write.
Hint: If you don't know what the acronyms in the first paragraph mean, this is not for you. Hire someone who does.
With the common availability of Virtual PC, creating an MSGINA.DLL has gotten a lot easier. You would create a VM for your test instance of Windows, and set it up to use undo disks. After installing your test MSGINA.DLL, if it should crash your instance of Windows, it's no big deal, as you can return to a fresh copy of Windows very easily.