AvCRTd.lib was compiled using the VS.Net C-runtime libraries and debug info which aren't compatible with the ones used by Visual C++ v6.0.
If you wish to use Visual C++ v6.0 you can edit the file AvCRT.h and change the line:
#pragma comment(lib, "AvCRTd.lib")
#pragma comment(lib, "AvCRT.lib")
You'll still get the defaultlib warning, but otherwise it should be ok.