There are times where it is helpful to test your CRM changes logged in as a different user. This will allow you to see everything that this user would experience.
Of course you can physically log on to the users machine, but a better way is to run a simple batch script that will start the CRM web client and prompt you for the users password.
The contents of the .bat script would look like:
runas /user:LITWAREINC\PaulW "C:\Program Files\Internet Explorer\iexplore http://moss:5555/loader.aspx"
You would supply your own CRM instance and user information. You do need to know the users password to test this way.
If you need to test specifically how something looks iwith the Outlook client, this won't help you... you'll still have to log on to the users machine and start Outlook.