On the Wine mailing list, there is some interesting information on Leopard's apparent ability to load basic Windows binaries. "When tracking down a crash in the kernel32 loader test, Dmitry found a bug in the Mac OS loader when Wine tried to load his dummy PE file. Upon further research I found that the Mac loader seems to have its own undocumented PE loader built in. I did some further testing with a Windows binary and got some really interesting results." The first thought was that this was a remnant from Mac OS X' EFI support, but upon further investigation, this really seems like new, Leopard-specific behaviour: "This is new to Leopard. On Tiger, dlopen rejects PE files as expected. The Wine testing that Steven was originally trying to do would probably not crash on Tiger." Apparently, Apple is trying its best to hide this behaviour.