Zimbra installs by default to the wrong installation folder in Windows. The Documents and Settings/Users folders is for user specific data components of programs and data, not for installs. Yes, I know I can change that, but the typical user will not.
This is a red flag to experienced users that the coders do not understand the platform they are writing to, and when I use this app that is exactly the reaction I have. That separation is there for a good reason. Yes, I realize other OSes do write all their programs exclusively to the users home directory, but Windows got it dead on right by putting program installs in one place, and user data in another. If the app coders aren't willing to take a platform seriously, why should I bother keeping that app around? Especially when there are better performing options that do put that thought into their app?