Completely untrue -- SOME viruses are .exe files... some others are .dll files... some others are VBScript files... some others don't come in file form at all.I love Macintosh because all of the viruses in the world are EXE!
In its current state, Darwine for PPC does very little. It can be used by Windows developers to recompile their apps for PPC without abandoning the Windows APIs. Currently I don't think it can run any Windows apps that have not been specifically targeted for Darwine. (But I haven't checked on it in a while; maybe their QEMU integration has reached a useful level at this point.)On a related note, what does WINE do on OS X, if it's not an emulator?