Hey snakes1100,

Go Into:
AdminCP --> Templates --> Default (or what ever set your using) New Posting Templates --> newthread (also newreply)

And Heres Where the code is:

newthread
Search For:
<textarea name="message" rows="20" cols="$textareacols" wrap="virtual" tabindex="2">$message</textarea>

newreply
Search For:
<textarea name="message" rows="20" cols="$textareacols" wrap="virtual" tabindex="2">$message</textarea>

Then the edit the bits that i've put in red.

Enjoy