From Wine HQ [1 ]: "Wine is an Open Source implementation of the Windows API on top of X, OpenGL, and Unix.
"Think of Wine as a compatibility layer for running Windows programs. Wine does not require Microsoft Windows, as it is a completely free alternative implementation of the Windows API consisting of 100% non-Microsoft code, however Wine can optionally use native Windows DLLs if they are available. Wine provides both a development toolkit for porting Windows source code to Unix as well as a program loader, allowing many unmodified Windows programs to run on x86-based Unixes, including Linux, FreeBSD, Mac OS X, and Solaris."
peterc 2008-06-13: getWindowsAPIVendor is a small but handy proc for detecting which win32 code base your app is really running on: Wine, ReactOS or Microsoft Windows. This can be used for tuning your app or informing the user of support/non-support.