Is possible/plausible to not have the domain name as part of the username in the user tables?

 While Active Directory works great, I am finding that another extension that I use (Document Exchange) does not work 100% because of the domain\username values for the Username.

 More specifically, the problem occurs when trying to establish a WebDav connection through Windows Explorer.  When a user tries establish this connection and passes his/her username as "Domain\Username", Windows Explorer drops the "Domain\" part of the user name from the request header, which in turn causes the Document Exchange WebDAV authentication to fail. However, the WebDAV works when the user is a non-domain user.  Unfortunately, all of my users are domain users.

This is not a limitation on AD authentication - more likely a limitation of Windows Explorer's WebDAV integration as well as Document Exchange's non-consideration of folks using the AD authentication and the effects on the  Username field in the users table.  However, Windows won't be rewriting explorer anytime soon, and Document Exchange does not provide the source code.  Hence why I am inquiring here.

 If the changes are possible (even with a mod in the code) could you possibly share some insight as to what the side-effects are within the rest of the system (if any) and what potential pitfalls may occur due to this change (if any).

 Thanks!

A code modification is one thing I was considering.  Instead of simply stripping the domain from the username upon registration, could we not add an additional column "Domain" to the users table?  That might help to solve username collisions - as you had mentioned.