Correct download link:
http://code.google.com/p/gimp-normal...2.zip&can=2&q=
You forgot it:
How to install:
To install, extract the normalmap.exe file to your GIMP plugins directory.
This directory is usually located at:
C:\Program Files\GIMP-2.0\lib\gimp\2.0\plug-ins

Then extract the 3 dll files to your GIMP bin directory.
This directory is usually located at:
C:\Program Files\GIMP-2.0\bin