Administrator in Vista

I'm trying to replace a file for a desktop application. Vista is refusing to allow me to do this, telling me to contact my administrator for permission. I am the administrator, the file isn't in use (nor is the application) and I cannot figure out how to do this. Any ideas? Thanks in advance.

 

You must take ownership of the file prior to deletion.

There are various ways....the easiest being this:
http://cid-a4b0f9235271a2fa.skydrive.live.com/self.aspx/XPero Utilities/TakeControlb2.zip

Unzip it, run the program as admin (right click), and then browse to the file in question.