How to add a new user field that is large like a multi line text area but cannot be edited

Hi,

I would like to add a new user field to my register page that is large like a multi line text area but cannot be edited (i.e. no facility to add links, make text bold, underline, etc).

If you see my register page http://greenscotland.org/register/ you will see the extended description box. I would like a large area like this so that users can write a long text comfortably but I do not want them to be able to add url links of their own.

Is it possible to remove the option to add links from a multi line text area or instead is it possible to insert a larger text box?

Thanks!