How should I ensure that my Visual Studio installer updates DLLs when installing an older version?

Question

I recently noticed that my installer (VS 2008) does not remove the DLLs during uninstall. This is not too much of a concern to me but the following is a concern: when I install an older version of my software, it does not overwrite the DLLs -- it keeps the newer version.

When I am rolling back my system to an older version, I would like everything to roll back. What is the best way to accomplish this? Do I need to create a custom action to remove the DLLs at uninstall to be safe, or is there another way to remove them, or is there a setting to force the installer to always write the DLL.

Answer 1

First you should ask yourself why didn't the installer remove the files, because it should and if it didn't then it's a BUG (or that the setup is waiting for a reboot to remove the files).
You can run you MSI with logging in order to discover what's going on there:
msiexec.exe /i /l*v