Zach has the best chance of being able to review, if only because he can probably build the installer. I've added all the Windows experts just in case. There's quite a bit of MSBuild magic involved here though - I have trouble getting good reviews of this kind of change at work :(

For whoever is looking - the InstallFiles items are processed by getting all the Included files, stripping SourceBase off the start and replacing it with Source (so a nop in this case) and including that file in the installer. The file is installed into Target (which is actually a directory reference into the installer, but DLLs is as self-explanatory as it seems) plus the relative path from TargetBase to the original filename. In this case, the old TargetBase was too short and so the file was installed with the last directory segment; after the fix the last directory segment is excluded. (Yes, the Source and SourceBase changes aren't really necessary, but changing them to match will avoid unnecessary questions in the future.)

I should really add more documentation about this... Tools/msi/readme.txt has a bit, but not at this level.