Integrate Members-Only Package Into Existing Website

[flyingspatulas]

I would like to implement a members-only/paid subscription system on my existing website. Basically I want members to have to pay a monthly/yearly fee for access to certain sections of the site.

The three sections I want to include use three different scripts on three different domains/subdomains:

Section 1. Wordpress in a subdomain (http://www.robert-pattinson.co.uk/press/)
Section 2. phpBB in a subdomain (http://www.robert-pattinson.co.uk/forum/)
Section 3. vShare in a domain (http://www.robertpattinsonmedia.co.uk/)

I do not want to have to redesign/recode/etc. these sections if at all possible - I would like to be able to integrate the members-only system into what is already there.

Is it possible to set up one system that will allow my visitors to subscribe to and log in to all three sections? If not, is there at least a program that will let me do this for the vShare domain?

I would appreciate any help you can offer. My level of expertise in this area is very low, so simple explanations would also be helpful. :)

I've included my website information below. Thanks in advance!

Website: http://www.robert-pattinson.co.uk/
Host: http://www.inmotionhosting.com/
Server: dedicated server w/cpanel
PHP version: 4
MySQL version: 5

[KGCustoms]

There are a number of members-only area scripts available, all of which require their own tweaks - but the easiest thing to do would be set up your choice of members area script in whatever language you'd like (PHP/HTML/etc) and integrate the necessary code into your existing pages (PHP would use something like

<?php include (../members.php); //your existing code goes here ?>

for example).