|Hi Peta, herewith some thoughts:-|
a) as Dave suggests, you should consider replacing the keyboard.
Inexpensive oem kb's can be found on ebay or amazon
Possibly youtube has a video on how to fit.
b) look under programs/accessories/accessability for the on-screen keyboard
c) google 'simulate enter key' and there may be an answer for you.
Please advise back on what you decide.
It might have helped if you had advised the laptop's make and model.
Good Luck - Keep us posted.