Custom Installation

[C# Programming]

Hi,

I want to perform an action before the beginning of an application installation.
I tried to override the event OnBeforeInstall (in the AddInCustomAction class) but I see that when that event is raised my files were already copied to the target directory.

The reason for what I want to do is:
I have a previous version of the application (without setup; just an exe) written in MFC.
Now I rewrite the application in C# .Net VS 2005, and the installation is done via a setup.
I don't want to change the name of the exe and nor the name of the Target directory.
so what I want to do is:
before the installation begin:
check that the previous verion doesn't exist.
if exists, remove the old exe
continue the installation

Any Ideas How can I do this?

Thanks,