I can tell you that the majority of the ISP are using NAT and you cant go further than knowing someone ISP provider
Not exactly. NAT is merely a break point between the public IP address space and the private IP address space. Virtually all ISP's assign a public IP address(accessible from anywhere in the world) to its dialup/dsl/cable users. Places where you would likely receive a private IP address is a "wireless hotspot," such as in a coffee shop Also, if you are using a Linksys router off of your cable modem, you are using NAT. Instead of your personal PC acquiring the public IP address that your cable internet provider gives to you, your router is assigned it instead. Your router then uses NAT to transfer back and forth the info you request from the web to your PC which is located in the private IP address space. The majority of home routers use the 192.168.X.X space for all of your PCs. If you surf from multiple computers that connect to the same router, you will notice that your "IP address" on JWD remains the same. This is NAT working. Even though your IP addresses are different between computers on the LAN side of your router's network, the public IP address that is assigned to the router remains the same. This is what the world "sees."
For the folks who wanted to know how this tracking works, I'll go ahead and give you the rundown again. First off, get yourself a webserver that you can view the logs on(run it off your home pc - that's the easiest). Full detailed logs are needed(if you use apache, just alter the conf file to allow full logs). Throw up a small transparent .gif file. The one I use is only 1x1 pixels and is 58 bytes in size. Insert the url of this transparent .gif into a post as a picture. The only way someone will be able to see this .gif is by looking at the html source for the page. Otherwise, it is completely invisible. Now, when someone replies to the thread or to your post, a log entry is added to your webserver that shows their public IP address, the url they are replying or posting to, their operating system, and web browser along with a timestamp at the front. You simply correlate the timestamp to a reply. In the logs, most posts will even show up as a "post" or "reply." It's all quite simple to do. I wrote about this a while ago but I don't think anyone took me seriously. Probably because you have a 50/50 split of people who say it cannot be done and the other half saying, "can you?" Of course, there are the very few who know it can be done but may not be saying anything to keep it a secret.
Want to know what that little transparent .gif file looks like? It's right here --->
That's it! Nothing too technical at all.