Help what have I done

Right my cat turned of my MacBook during an update so I reinstalled osx but th start up disk was a wd elements I have I have then turned it on and hold the option key and click on the internal hd but I seem to get the apple logo and it doesn't load I then tried installing osx on the the internal hd but it wont let me. I have all ready lost everything but what can I do to get it back to the desktop so I can then updated it put the apps and iTunes stuff back and then use it help please

Sorry for poor grammar as I am on the iPhone

What version of OS X are you running? Recovery options are different depending on the version.

Lion

When the machine was running good it was ruining on
Lion but whenever re installed the disc it was on snow leopard. When it fixes will I be able to get lion back

So, here's what you did - you reinstalled the OS using your Snow Leopard disc onto your external drive. What you actually wanted to do was use Lion's recovery options to reinstall Lion.

Turn the machine OFF. Disconnect the external drive.

Turn it on and immediately press and hold Command + R.

This will boot you to the Recovery Options menu. From here, you should be able to reinstall Lion to your internal drive.