As Wallace says make sure the plugin luce.exe is in your Gimp 2.8 user plugins folder Remember it starts with a dot and is a hidden folder C:\Users\"yourname"\.gimp-2.8\plug-ins.
Really need more info:
Is your Windows installation 32 or 64 bit ? The Gimp installer contains both versions and installs accordingly.
Where did you get the luce.exe plugin ? I pulled a 32 bit version out of my archive and that does not work at all. Better luck with a 64 bit version. This Win 7 - 64 bit / Gimp 2.8.
Attachment:
luce.jpg [ 165.99 KiB | Viewed 535 times ]
Your error messages look suspiciously like 32 bit..and you are probably getting them by trying to run the plugin directly. ( (2) as console above) Any Gimp plugin has to start from the Gimp menu system, in this case Filters -> Light and Shadow -> luce. (1)