It helps to have some experience with VBA coding, but the instructions are clear and no other applications are needed other than the Visual Basic editor that is built into Outlook.
Eric Legault is also a blog contributor at Office Zealot.com The source code for the MSDN article can be downloaded there. It includes the complete form as well as the code modules.
... "image viewers that use a Multiple Document Interface (MDI) are best suited as a custom viewer. It's better to have one application handle several open image windows than individual windows cluttering your Taskbar! A perfect application for this scenario is the Microsoft Office Photo Editor, but it is no longer bundled with Office 2003."
Microsoft has replaced Photo Editor with a new photo editing and cataloging program in Office 2003 and 2007: Microsoft Office Picture Manager.