Quote from the cookbook :
To prepare your environment for using Eclipse in Windows, you should also create a batch file and use it to start Eclipse.
To create that batch file, follow these steps.
Locate the folder where qgis_core.dll resides in. Normally this is C:\OSGeo4W\apps\qgis\bin, but if you compiled your own QGIS application this is in your build folder in output/bin/RelWithDebInfo Locate your eclipse.exe executable. Create the following script and use this to start eclipse when developing QGIS plugins.
call "C:\OSGeo4W\bin\o4w_env.bat"
set PATH=%PATH%;C:\path\to\your\qgis_core.dll\parent\folder
C:\path\to\your\eclipse.exe
End quote
In your case as you have install a standalone version it's in the install folder of Qgis as this :
call "(Qgis install path)\bin\o4w_env.bat"
set PATH=%PATH%;(Qgis install path)\apps\qgis\bin
After setting up your batch file use it (by double click on it) to run eclipse. So your environnement will be set up and eclipse will find everything it needs to run you code.