I don't know about installing a visual captcha, but if you can get some help with the code a 'text captcha' is an easy thing to add. Heck even adding a visual captcha will require some programming skills, Basically it'd go like this:

On your form you add a new text field with a message "What color is red?". Obviously the visitor is expected to type 'red' as the reply. You make the question be whatever you want. Who was in the White House when Clinton was President. Five comes after what number (4 letters). Are you a spambot?

So now when the form is submitted you check that field first. If the answer is not exactly what you want then you can either just ignore everything or provide a page telling the visitor they missed an important field.

Anyway for someone familiar with coding a form page in general adding this detail shouldn't be a problem. Eventually you might get some spam, but so what: you simply change the question and answer and you're good to go again.

I guess I need to find a form coder. There are some scripts on the web for doing this but they want too much mula. I will look around.
Thanks,

Expanding onto EdBs suggestion, have a array that contains a bunch of questions and their answers

 $q_and_a = array( array('Are you spamming me?', 'no'), array('Whats the number after 4','5') );

And in your form have something like this

<input type="hidden" name="question_num" value="<?php echo $the_index_of_the_question_we_chose; ?>" />

And for $the_index_of_the_question_we_chose just use php's random function to pick a index.

You should understand all that, if not, bout time you start to ;)

Edit & Offtopic: Geeze a awful big post for one that only contains 2 lines of code...

I just found a script that I purchased for 20 bucks that allows you to put captcha into any php driven form. There is the url to the script:
http://websitedatabases.com/captcha_image_security/captcha_image.html

Now I just need to get it to work!