What is it?

ANTIVIRUS.EXE may be part of a legitimate application however at the time of this writing it has been found to be associated with several internet worms, It is therefore recommended to thouroughly scan your PC with up-to-date antivirus applications.

What does it do?

Viruses do bad stuff ;)

More info:

Keep an eye on [url=http://www.google.com/search?hl=en&q=ANTIVIRUS.EXE]this[/url] Google search for associations and help to remove any worms related to "antivirus.exe" Compare the discriptions of the worms, use appropriate applications to identify any infected files prior to any attempt at manually removing them?via the instructions provided by some of those web pages.