It depends on how you have access control and logging setup in MS Proxy, If you have the Logging on, Access control enabled and user names added to the proxy ACL's then the logs will show the User name and the m\c netbios name or the m\c IP, Date Time, any site visited and the object downloaded. The log files are saved as comma separated values and can be opened in any word processor or can be imported to a spreadsheet or database (even MS Access) to make reading and searching simple. One thing to be aware of is if there is a dash instead of a user name\m\c ID it will be the URL\Object cache refreshing automatically. You have to be aware of the refresh if your are on a dial-up connection or pay on a bandwidth used basis as this can seriously rack the bill up
Hope this helps