Paolo,

The plug-in tutorial explains in section B:

B - How to install a plug-in
1 - Windows
To install a SH3P file in the plug-in folder, simply double-click the file.

Maybe you missed this?
If that doesn't work, you can do the reverse procedure for uninstalling:

C - How to uninstall a plug-in
1a - Windows Vista and Windows 7
Remove the plug-in from the folder
C:\Users\user\AppData\Roaming\eTeks\Sweet Home 3D\plugins

That means, that you copy the plugin to this directory.

If you want me to look at your file, send it to [url=mailto:[email protected]]me[/url] and explain what I should look at.

Hans