HTMLEncode all the user input

Apologies if this has already been asked and answered but I cannot find the post.

I am using CKEditor 3.5.2 (revision 6449) in an ASP>NET 4.0 Web App and I cannot seem to HTML encode just the user input. for instance

A user enter "Hello World" in the editor and I am saving this in my DB as

<p>   Hello World</p> 

Not 100% why the space after the paragraph open tag but thats not my issue if the same user enters

<script>function hackme() {alert("Whats up!")}</script><input type="button"; value="Completely safe button" onclick="hackme()" />

it is saved to my db as

<p>   <script>function hackme() {alert(&quot;Whats up!&quot;)}</script><input type=&quot;button&quot;; value=&quot;Completely safe button&quot; onclick=&quot;hackme()&quot; /></p>  

The quotes are encoded with no interaction from me but how would I encode the entire string so that the html that they entered is fully encoded e.g.

<p>&lt;script&gt;function hackme() {alert(&quot;Whats up!&quot;)}&lt;/script&gt;&lt;input type=&quot;button&quot;; value=&quot;Completely safe button&quot; onclick=&quot;hackme()&quot; /&gt;</p>  

note the paragraph tags have not been altered

Thanks in advance