Symantec has provided a fixtool to remove infections of W32.Nimda.A@mm.

There are several variants of W32.Nimda in general circulation. Two of the most common are:

W32.Nimda.A@mm
W32.Nimda.E@mm
Symantec Security Response has created separate removal tools for both of these threats. The tools are not interchangeable. Before you can use a removal tool, you must know which variant has infected the computer. The tool that can be downloaded from this document is designed to remove infections of W32.Nimda.A@mm. (Note the .A). It will not remove infections of W32.Nimda.E@mm.