so i hit the same exception, here is how i solved it.

environment:
windows 7 enterprise 64 bit
python 2.7.5 64 bit
visual studio 2008 32 bit

issue:
pip installs failed with the above exception.

solution:
there are two parts.
1. install 64 bit components to vs2008
2. modify the PATH to point to 64 bit vs2008 bin folder

to confirm is this solution will help you:
check if there is an amd64 under your vs2008 bin folder:
C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin
if yes, this solution will not help you.
if missing follow the steps below.

step 1.
control panel
select Microsoft Visual Studio 2008 Professional -ENU
window Visual Studio 2008 Maintenance Mode is opened
click through to and select Add or Remove Features
Under Language Tools->VC++ "X64 Compilers and Tools" should be unchecked.
if it is checked, skip to step 2.
check "X64 Compilers and Tools", Update.
you may have to provide the VS2008 installation CD.
confirm that update creates bin\amd64 subfolder.

step 2.
add 64 bit subfolder to your path.
VS2008_HOME=C:\Program Files (x86)\Microsoft Visual Studio 9.0
PATH=%PATH%;%VS2008_HOME%\VC\bin;%VS2008_HOME%\VC\bin\amd64;
open new command window to receive new PATH changes.
pip installations should no die with the ValueError.