How can we ID the client computer w/out cookie or IP?

[ultranet]

Hello all

Actually we working on a project and at this point we are struggling with one single issue.

The project is web/browser based and requires our server to remember each computer, but we don't want to use anything that can be changed (eg. cookie, IP). We need a method that will stay on the computer as long as possible. And also it has to be cross browser/OS. We don't want to do browser plug-ins because that would just be too much for to provide & update for each browser.

It doesn't matter what programing language, we just need a solution. Thank you and happy new year