This problem can arise with different extensions, as it was reported, and doesn't seem to be bound to a specific one.
So, other people will not find the same problem as you.
We didn't come to a point, in how this problem works.
Indeed, HFS doesn't bind to .msi files, but to all files (through the "*" symbol).
So, for some files, they get associated automatically to HFS because of this.
It has to do sth with the registry, but i'm not an expert and didn't find an explanation.
Maybe someone else will...