Unfortunately, if you want to download a pre-compiled Boost for Visual Studio, you are required to register for an account with boostpro.com. When I was looking to download Boost for Windows recently 1.38 was not yet available precompiled and I personally did not want to register for an account to download free software, so I built it myself. Fortunately, the process is very simple:
bjam threading=multi --prefix=C:\boost install
This will build everything except boost::python and will not have ICU support in boost::regex. Otherwise, it will install it into c:\boost.