Behavior on Terminal Server 2003

Ok, I’ll try again with another question:

We have terminal server 2003 and thin clients; users are getting the full desktop.

Just now, a user checked his email via Thunderbird, and it stuck at a specific email (18 / 32). No messages on his screen, no nothing…just waiting.

I went to the server, logged in locally as admin, and find a large rotating radiation symbol saying “virus found”!!

??

I clicked delete several times, the message went away, and the user got the rest of his email.

Shouldn’t that box popped up on the user’s desktop? How can I make it do so?

Please help…