Some customers are reporting problems with start debugging an application after VS2003 SP1 has been installed. Here is the scenario:
You have a managed project open (like, for example, a C# class library) and in the Project Properties, under Configuration Properties | Debugging you have Debug Mode = "Program" and Start Application = <some application that will load either this dll or other managed code you wrote> and when you F5 you are getting the an error messge saying that your .exe was not found.
If you are running into this issue please check to see if the .NET Framework 2.0 is installed on your machine (i.e. you have the following directory on your machine: <system drive>:\WINDOWS\Microsoft.NET\Framework\v2.0.50727). If you have this installed, here is a workaround you could try:
Create a file called <your exe's name>.exe.config with the following contents and place it next to your exe on your machine:
<requiredRuntime version="v1.1.4322" safemode="true"/>
This will force your exe to load the 1.1 version of the runtime instead of the 2.0 one which otherwise would be loaded by default since it's the latest version available. The VS2003 debugger does not support debugging against the 2.0 version of the .NET Framework hence the problem.
Hope this helps!