What's the best way to confirm & track actual usage & time stamps of a users internet activity?

I need to look at an employees internet usage for /adult content and other usage. I need to have actual proof with URLs, timestamps, times visited, time spent on a website, etc. Computer being used is Windows Vista w/ IE7. I've looked through the history and cookies and see some unauthorized activity but haven't found all the details I'm looking for and a way to export/back them up. I've tried index.dat yzers but there are ~15-20 index.dat files found. I haven't found an yzer that will provide the essential proof needed that can export/back up the usage/history easily. Any help would be appreciated.