If you're having acaddoc.lsp as Ayman says, find below a lisp routine that we use in our office which prevents AutoCAD from generating acaddoc.lsp every time you open a drawing. And you better add acaddoc.lsp to your antivirus definitions.
http://www.mediafire.com/?exrdr91o30s4c85
The routine works in 32-bit. Try Google for 64-bit.