How do I start an application automatically before the Novell login client or windows XP/NT/2000 login??

...not sure why you would want to do that, but you could attach some sort of batch file or executable to the windows shell. It's somewhat unstable but i've seen it done.

These two keys are read before winlogon starts. To learn how to use them you can read up on M$ support or technet about service order loading and control, and the Session Mgr.
1. BootExecute HKLM\System\CurrentControlSet\Control\Session Manager
2. Services HKLM\System\CurrentControlSet\Services
It's a pretty sensitive time in the order of things; if you load too early you'll get some error because of the loading, starting of services.

commented: Correct and brilliant answer +9