Determining Windows Username in an BSP Application?

Hello Experts-

Do you know of a technique by which I can find out the Windows username of the person that is using a BSP application on the Internet (or even an Intranet)?

In my BSP application I need to be able to find out the Windows login of the user that is using my BSP application on the web or within the corporate network.

Thank you,

- Vik.