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)
Your ISP should have a log with your visited sites and all of your network transfers. Try contacting them.