A few customers have asked what the ramifications are of developing Microsoft Office Excel and Microsoft Office Word solutions on a computer with the following products installed side-by-side:

• Microsoft Visual Studio .NET 2003
• Microsoft Visual Studio 2005 
• Microsoft Visual Studio Tools for the Microsoft Office System, Version 2003 
• Microsoft Visual Studio Tools for the Microsoft Office System, Version 2005

Word 2003 and Excel 2003 will load the latest version of the Microsoft .NET Framework installed on the computer (in this case, the .NET Framework 2.0) before running managed code extensions. So, there are no significant debugging or security issues for Visual Studio Tools for Office, Version 2005 solutions. However, if you're developing a Visual Studio Tools for Office, Version 2003 solution, you need to be aware of the following issues.

First, let’s look at debugging a Visual Studio Tools for the Microsoft Office System, Version 2003 solution with the .NET Framework 2.0:

1. Start the solution by clicking Start Without Debugging on the Debug menu in Visual Studio .NET 2003, or start Word or Excel and then open the solution's document. 
2. Once the solution is running, start up Visual Studio 2005, and click Attach to Process on the Tools menu. 
3. When the Attach to Process dialog box opens, select Winword or Excel in the Process list and then click Attach. The Microsoft Visual Studio 2005 debugger opens attached to your solution.

If you instead want to start debugging before the document's Startup event is fired, the steps are different:

1. Open Word or Excel and then open the solution's document (in order to get Word or Excel to load the .NET Framework 2.0). 
2. Close the solution's document but leave Word or Excel running. 
3. Attach to Winword or Excel with Visual Studio 2005. 
4. Open the solution's document again.

Next, you must set security policy for the .NET Framework 2.0 for new solutions to run, whether they are Visual Studio Tools for Office, Version 2003 or Version 2005 solutions. However, it's important to note that any security policy that exists as part of the .NET Framework 1.1 will be brought forward automatically when you install the .NET Framework 2.0.

Many thanks to Peter Torr, Harry Miller, and Eric Carter for their help with this post.