Unable to install scripts

I have some problems understanding how to install scripts to blender. I have installed blender, i downloaded the zip and extracted the contents to c:/program files/blender.

In the settings I then choose a folder for my scripts (d:/blender/scripts), saved default. Then I clicked install script. I got no errors.

But now when i search for the script, I can´t find it.

The script is called mesh_fake_knife.py.

What am I doing wrong. I have also been unable to install the xplane2blender script.

blender 2.56a beta, downloaded today.

If it doesn’t show up in the list of addons that you can select in the User Preferences / Addons panel then more than likely the script was not compatible with the blender version you are using.
Searching for that script name gave web pages from May last year, blender 2.56a came out the start of this year. If this is the case, unless the script was updated very recently it just won’t work with the blender version you have.
Unless a script came installed with the blender version I have I never start with the assumption the script will work.

With regards to fake_knife, it is bundled (along with a ton of other add-ons) in recent fillicis builds on http://www.graphicall.org.