.aspx maybe? Failing that, link us up.

Thanks Guys,
I thought it might be helpful if I explained in more detail, just what I am trying to do.
I have an Over 50's site <
www.Age-Net.co.uk> It runs on a Windows asp server so the Home page is index.asp All other pages are '
www.root/folder/name.htm'. The site is large enough to be to be time consuming and I need to make it more easily manageable.
I need to migrate the site across to a new template and use includes for the navigation bars, footer and possibly also the advertising blocks - Adsense etc. This is going to take weeks rather than days.............
First though, I want to introduce a new section to maintain reader interest.
So, I have opened a new section folder, wwwroot/new_sub_section/ which contains new template, CSS & image files and a new index page with four linked sub pages. It also contains includes for navigation and footer files. The sub index page displays the includes perfectly when viewed in Dreamweaver but when up-loaded to the server, they no longer show.
I tried .aspx for the sub index page Granty. This works on the single page when uploaded to the server, but not for the other four pages I have it linked to. Changing them to .asp or .aspx just generates a 500 error.
Obviously, I am confused! Seems it might be more efficient to just re-do the Home page with the includes and then work through each section of the site. I will keep you posted.
Thanks all.....
Bob
If my explanation is unclear

at the very foot of
www.age-net.co.uk Home page there is a 'developer's link' showing the draft new section I am trying to introduce.
Bob