Deployment Installer problem

I was unsure where to post this, so I do apologise if it is in the wrong forum.

I have been having a wierd issue, no idea where the problem lies.

I have setup launch conditions, my application has some requirements on the target machine. The launch conditions are based on file and registry search.

Registry search works fine, and if there is one key/value that doesnt match, installer fails - just want I want :)

As for the file search, this is where things go wrong. I am running the installers on my test environments which is a WS2003EESP1 computer and WinXP PRO SP2 computer, both plain vanilla installations.

The problem is, these files need to be on the computer, 2 files in particular. I have specified the properties appropriatly (filename to search for, version number, folder to search in and so on)

If that file does NOT exist, the installer continues on as normal - this is not what I want. if a file does not exist, I want it to stop just like it does with the registry match/search.

Does anyone know why What can I do to make this work Am I doing something wrong

Many thanks!