Forwarding numerous website addresses to one

I am not sure if this is the right area to ask this, but I am a complete novice at web hosting , so if any of you can help me I would be very appreciative. Forgive me if my question is dumb

My primary webserver is running win2000.

I host several websites on my webserver, and have ns1 and ns2 addresses set up. Now one of the sites www.thisite.com (made up example) needs to have www.thisite.org and www.thisite.org.uk point to it as well. I have all the websites registered and pointed to my webserver (via the ns1 and ns2 addresses). Only the original www.thisite.com is set up as a website, I have tried to add the other addresses in the advanced properties tab of the primary site, giving them the same IP. This appears not to work (which does not surprise me as it seemed too easy). What do I need to do!!! Please any help, as I don't want to set up browser forwarding in the individual sites, this is too slow...

You need to configure aliases for your website in your webserver config. You need to tell your web server that those other 2 domains are the same site. All 3 domains need to pull files from the same directory.

As for DNS, all three domains just need to point to the same IP.