How do I determine which operating system is running

The Environment class in the System namespace has this information. [C#] string versionText = Environment.OSVersion.Version.ToString(); [VB.NET] Dim versionText As String = Environment.OSVersion.Version.ToString() The Version property has member properties such as Major and Minor that give additional information. Note that XP is windows version 5.1

How do I paint in my mdi container, a logo, for example?

You should not try listening to your MDI container Form’s Paint event, instead listen to the Paint event of the MDIClient control that is a child of the mdi container form. This article provides you a detailed example: Painting in the MDI Client Area