detecting user log in and user unlock screen

I have a program which always runs in the background. It is also executed automatically each time the computer starts. I want it to recognize when a user logs in, or when a user unlocks his screen, so that it can display a welcome screen. How is this possible?
Does windows send any message to programs when someone unlocks the screen?

thanks
anoop

You cant detect when the workstation is unlocked but you can detect when there is activity. What OS is it running on and does it need multiple S version compatibility?

Quote:

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Originally Posted by RobDog888

What OS is it running on and does it need multiple S version compatibility?

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Its meant for win xp. I didnt understand the second part of the question...

I got the vb.net code for this:
http://www.codeproject.com/Purgatory...lockunlock.asp

but i cant figure out how to do the same in vb6