Discovered a couple of minor errors in pcbuild.sln and pythoncore.vsproj while working out how to compile 2.5 on Windows using the VS C++ Toolkit for the bug day (no Visual Studio at home). FWIW, I eventually ended up using Nant (using the <solution> task).
Nant couldn't build 2.5 without the fixes - basically, _ctypes_test didn't have any dependencies, and so was being built first. And the GUIDs for pythoncore were different between pcbuild.sln and pythoncore.vsproj.
I've attached the fix to the bug report.