The problem is that Vista has some safety features associated with setting permissions on the Program Files folder. Basically, even if you are an admin, you can’t change permissions on some folders like Program Files and Windows folder itself. This causes initdb to be unable to create some folders and the database cluster. What this means for you is that you need to install PostgreSQL in another folder that is not inside Program Files.
The solution and how to fix this issue can be found in this URL