I am using boost 41. When building 41 I was using compiler version as 9.0 I built boost 42 in another directory, and for this built I used compiler version as reported by cl.exe. In my case it is 15.00.30729.01, so when using bjam I entered msvc-15.00 as toolset. Boost 42 was built successfully, but my program now does not link with linker complaining: fatal error LNK1104: cannot open file 'libboost_system-vc90-mt-gd- 1_42.lib' All my directories for boost 41 and boost 42 are the same, except that all libs in boost42/stage/lib have 1500 as part of the filename. When I copy "09" libs from boost41/stage/lib to boost42/stage/lib project complies successfully, so I know that dirs are not the problem. Question: how to resolve this problem? I can rebuild with 9.0 as compiler version, but I would like to undestand why 15.00 does not work.