For 32 bit boost, start a 32 bit command prompt. (on 64 bit Windows you find this in C:\Windows\SysWOW64\cmd.exe). Then run "bootstrap.bat" from the Boost root directory. This creates an appropriate b2.exe. Then run
b2 link=shared address-model=32
your command as before. (Although I noticed you tagged boost-thread; to build just the thread libraries, append--with-thread
to the command).
For 64 bit boost (on 64 bit OS), start a 64 bit command prompt (C:\Windows\System32\cmd.exe). Yes I know that looks odd but, trust me. Run "boostrap.bat" again, then
b2 link=shared address-model=64