How to compile and use OS2API.LIB The order of the include diretories is important. First the standard include directory (WATCOM\H) Then the os/2 toolkit (WATCOM\H\OS2) Then win32 SDK (WATCOM\H\NT) Example: I:\WATCOM\H;I:\WATCOM\H\OS2;I:\WATCOM\H\NT For improved speed you may consider copying the OS/2 header files and modifying the calling convention. Watcom's standard calling convention is faster than _System. Compile all *.cpp files (except test.cpp) and put them into a library. When you compile you OS/2 application remember to call initFileTable(), initProcess() and initMemory(). An example is in test.cpp. The OS/2 source files will probably not discover that they are in fact running under NT