Question: I am in a position where I might have to prove that I made a certain amount of MB downloads from the Internet including webpages browsed to a court of law. Is there a way of finding this out from Windows Vista Ultimate. If I need to do this in the future is there a way of setting up Ultimate to audit my account to provide a trail of downloads ?

Answer: 
if you are using Internet Explorer, you may be able to recover information of interest to you from index.dat

> 
> **index.dat** is a file used by the Internet Explorer web browser. The
>  index.dat file functions as an active
>  database, which runs as long as a user
>  is logged on in Windows. It functions
>  as a repository of redundant
>  information, such as **web URLs**, **search
>  queries** and **recently opened files**.
> 
> 
> 

you can read the content of index.dat with [**WinSpy Index.dat Viewer**](http://www.softwarepatch.com/software/indexdat.html)
It completely depends on what you are using to download. Can you give us a bit more information about your environment? What browser(s)? Do you use download managers? What kind of downloads are you talking about? etc...

Your best bet is to set up some kind of logging proxy to run your Internet traffic through. This would record all of your Internet traffic and provide raw data for statistical analysis (sites visited, files downloaded, size of downloads...).

But even then, data in these types of systems are easily forged...