how to show message just after logon to computer (Win XP)

[BioHazard]

Can someone help me how to show a message to user just AFTER he/she logon to the computer? (just the way we can show a message to user BEFORE he/she logon, through the 'legal notice message' in registry).
I am using win xp pro and want to display a message to every user after he logons to my computer. Can someone help me how to do this from registry?

I am waiting for reply, and shall be very thankful.

[NoHero]

For the local user:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

For the global machine:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

In the format:

Value name= Applicaton name
Value type = String
Value = Path to application to start

[BioHazard]

thanks very mcuh for your reply, but I could not understand, the method you told is used to start an application at startup, but what I want to do is to show/display a message to the user just after he logon to the windows.
Just like we can show a legal notice message through registry to the user BEFORE he logon to the windows, I want to show a message right AFTER he logon.
Waiting for your reply.