If you've connected the PC to the Internet without having first
enabling a firewall, without having first installed an antivirus
application with current virus definition files, and/or before
installing the KB824146 Hotfix, you're very likely to have been
infected from any of the thousands of PCs on the Internet that are
constantly broadcasting the Blaster and/or Welchia worms. It only
takes a few seconds of exposure.
To stay on-line long enough to get the necessary updates, patches,
and removal tools, click Start > Run, and enter "shutdown -a" when the
next RPC countdown begins. This will abort the shut down. Also, make
sure you've enabled a firewall before starting, to preclude any more
intrusions while getting the updates/patches/tools.