VB.NET Visual Studio 2010 Express debug err: project Type.. Class Lib.. cannot

[Dave_B]

I use VB.NET Visual Studio 2010 Express for VB.NET AutoCAD 2013 programming on Win XP-64, Service Pack 2.  Visual Studio debug has been working fine but suddenly stopped working.  When I try to debug any of my projects, I get the message: "A project with an Output Type of Class Library cannot be started directly. In order to debug this project, add an executable project to this solution which references the library project. Set the executable project as the startup project."  I use the standard method for enabling debugging of visual studio Express projects, that is add startup program info to the vbproj.user file.

My VB.NET Visual Studio 2008 programs with AutoCAD 2011 still debug properly.

I'm wondering has this happened to anyone else?  Maybe a recent Windows update (which updated NET among other things) changed some switch that I can change back?  My Windows Forms applications still debug correctly.

my .vbproj.user file:

<?xml version="1.0" encoding="utf-8"?>

<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">

<PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'">

<StartProgram>C:\Program Files\Autodesk\AutoCAD 2013\acad.exe</StartProgram>

<StartAction>Program</StartAction>

<StartArguments>/b "C:\Documents and Settings\username\My Documents\ACAD\VB2010\plottingtools\script.scr"</StartArguments>

</PropertyGroup>

</Project>

my vbproj file debug section:

<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">

<DebugSymbols>true</DebugSymbols>

<DebugType>full</DebugType>

<DefineDebug>true</DefineDebug>

<DefineTrace>true</DefineTrace>

<OutputPath>bin\Debug\</OutputPath>

<DocumentationFile>plottingtools_13.xml</DocumentationFile>

<NoWarn>42016,41999,42017,42018,42019,42032,42036,42020,42021,42022,42353,42354,42355</NoWarn>

<StartAction>Program</StartAction>

<StartProgram>C:\Program Files\Autodesk\AutoCAD 2013\acad.exe</StartProgram>

<StartArguments>/b "C:\Documents and Settings\username\My Documents\ACAD\VB2010\plottingtools\script.scr"</StartArguments>

</PropertyGroup>

my script.scr:

netload ..\bin\Debug\plottingtools_13.dll

[Dave_B · Accepted solution]

A follow up: My PC OS & all software has been reinstalled: Windows 7.  The issue is not a problem for me now.