This is a reposting of an article I originally wrote on my Developing for Dynamics GP blog.
GP Power Tools – Administrator Tools Module can provide this functionality without needing customizations. (http://WinthropDC.com/GPPT)
Following on from my previous posts: Customising the Company Login window series Part 1 – Introduction, Customising the Company Login window series Part 2 – Visual Basic for Applications and Customising the Company Login window series Part 3 – Dexterity, here is a discussion about trying to create a solution using Visual Studio Tools.