Download this file to any convenient location:
http://registry.gimp.org/files/Resynthesizer_v1.0-i686.zip
Double-click to unzip the folder.
Double-click on the resulting folder to open it.
There are 12 files in there but you don't need the text documents. Select the other 10 (e.g. by holding Ctrl down while you click on each one in turn). Once they're all highlighted, right-click on any of them and select 'Copy'.
Now go to Computer > C (Drive) > Users > [your username] > .gimp-2.8 > plug-ins. Once there, right-click and select 'Paste'. Close the Window.
That actually installs a
set of plug-ins. The (full) Resynthesizer one is quite complex but the others work along the same lines. For more information return to th