.act to .bdy
It's just a VFS file; rename it to .VFS and open it with the vfs packager, or use milkshape, theres a decompile option under the tools menu.
RF2 site: http://realityfactory2.sourceforge.net/
RF2 tasks: http://sourceforge.net/pm/?group_id=179085
RF2 tasks: http://sourceforge.net/pm/?group_id=179085