email worm

Hi

I am the admin for the Electoral Commission of Namibia. Two Months ago were where attacked my a virus that disabled the Active Directory. I managed to get it under control with Karspersky Open Business suite. After having detected and deleted all viruses from the server and workstations, users finally managed to log in. At present I have two problems. One my network in extremely slow, and most of off users have received complaints that several copies of the same message is received after initial writing.

Kaspersky does not detect anything when scanning the mail boxes. How can I identify the type of virus. Please HELP!!