Hi Omaga,
you can try this....
when you initially created the cookie, you used this line -
setcookie("name", "value", "expiration");
To delete the cookie you would code -
setcookie("name", "");
alternatively you can add -
setcookie("name", "", time()-60);
This sets the expiration date that is in the past.
You can assign the cookie deletion function to execute upon a user hitting a "reset" button for instance.
Hope this helps
-Abi