Your
first screenshot already shows that you don't have Messenger Plus! installed or it wasn't installed properly, or the installation is damaged because of other things you did (like wrongly removing stuff, messing in the registry, using system restore in the wrong way, etc).
If Messenger Plus! is installed properly, you have have seen a proper 'Messenger Plus! Soundpack' icon instead of the 'unknown file type' icon in Windows.
If you see the 'unknown file type' icon, it most likely means that there isn't a program associated with that type of file and thus you wont be able to open the file by double clicking on it.
Simply re-install Messenger Plus!, so Plus! can re-associate itself with PLP files...
----------------------
Dispite all this, if you are able to run Messenger Plus!, you still could have imported the soundpack if you go, in Messenger, to:
Plus! > Sound Library > Import/Export > Import a Sound Pack
----------------------
PS: important notes for when you make and attach screenshots:
- Take only a picture of the important part of the screenshot. It is useless to attach an 1024x786 pixels big image for only showing 100x100 pixels.
- Safe the screenshot as a JPG or GIF. Don't use BMP, and certaninly not a BMP with 32bit colors (Even in MS Paint you can safe pictures in other formats than BMP).
Reason for all this is to safe space and bandwidth. Not only for you but for everybody else who wants to see the screenshot.
+300KB is seriously wasted bandwith when you could have shown the same thing with only a 2KB big file.
----------------------
PS: important note for when you download stuff:
Do not save the things you download to your desktop. This isn't only insecure, it will also make a big mess of your desktop. You wont be able to know what is what after a while. And most importantly, it will considerably slow down Windows.
If you store stuff, do it in subdirectories.