I am trying to build boost libraries on Windows 7 x64 machine using mingw. When I try to run b2
b2 --build-dir=\"C:\\boost\\build\" --toolset=gcc --with-python
This thread is a year old, but I had the same problem and got it working, so in case anyone else needs a solution, here's mine.
bjam was looking for a file called "boostcpp.jam" which didn't exist in the production version of boost. Luckily, you can find it on github.
https://github.com/iNiKe/boost/blob/master/boostcpp.jam
Download that file (or copy-paste it from your browser to a new file) and save it as "boostcpp.jam" in your boost directory (or maybe it's the location where you run bjam from...they happened to be the same directory in my situation) and run the command again. Hopefully it'll work for you too.