This is a very simple way of disabling the Ctrl+Alt+Del combination in Windows XP or running the program of your choice thourgh the all-migthy Registry.
I spent the last night programming a lot of things and reading many articles and I found tons of people asking for a way of locking the Windows desktop. A lot of articles talk about locking the mouse and keyboard but they all leave something behind: the Task Manager. Only a few articles addressed the subject. This article shows a list of ways of achieving this and thoroughly discusses one and presents the source. The two most known ways are subclassing the SAS (Secure Attention Sequence) window and writing a Gina dll. These are indeed really hard and time consuming tasks (the latter one being almost impossible).
Using the code
Using the Registry editor of your choice (for example regedit.exe) navigate to:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\taskmgr.exe
Now create a new alphanumerical value called Debugger and change its data to the path of the program you want to run with Ctrl+Alt+Del (try calc.exe or notepad.exe for instance).
If you want no action just change its data to something invalid (a space, the string "·$·%", "dontruntaskmanager"... you get the point).
And thats it! No SAS window sublcassing no Gina dll... It just can't get simpler.