I recently had to customize a Team Build script to build only one VS2003 solution and found that Nagaraju Palla's approach #2 in this post was the best way to do it. However, since I had no other solutions to build and this was a VS2003 solution, I had to remove the <SolutionToBuild> item from my TfsBuild.proj file; I could not use it to specify the VS2003 solution there because that item is expected to have VS2005 solution files. Later on I found out that those Team Build runs were not making it to the "Builds" report.
I had to make it work so I started troubleshooting it until it came to a point where I had to create a blank VS2005 solution; I checked it into the same folder where the VS2003 solution was and specified that VS2005 solution file in the <SolutionToBuild> item. This was the only way I was able to make the build runs show up in the Builds report.
Even though I gave it a very meaningful name (VS2005BlankSolutionForTeamBuild.sln) I was not entirely happy with having to add a file to the SCC Repository just for that purpose (an alternative was to create the solution file in my build script but I didn't like that either). After exchanging some emails with some Microsoft folks they explained to me what is going on there and then it all made sense.
I am not going to go into the details they gave me because it would not help you at all. I just hope that people are able to find this post when they need it.
I realize that I wrote this post assuming that the reader will have some experience customizing team build scripts and will know what I am talking about. If you need more details feel free to drop me a note through the 'Email' link on this blog and I will try to help.
Another thing that you may find useful when building VS2003 web projects in Team Build is this post from Jeffrey Palermo on how to remove the IIS binding from a VS2003 project file.
-OmarV