In an aspx page I get the Windows username with the function Request.LogonUserIdentity.Name. This function returns a string in the format \"domain\\user\".
I was suggesting to use regexpes but they would be overkill.
[System.String.Split](http://msdn.microsoft.com/en-us/library/b873y76a(VS.80).aspx) do the job.
string[] parts= username.Split( new char[] {'\\'} );
return parts[1];