I have a site collection set up at web app running at port 80. I have made the backup of the site collection content db using stsadm.exe tool. Now, I want to restore that backup as a new content db of a different site collection - the one set up at web app running at port 500. I have done the following:

1. Created a backup
2. Created new web app at port 500 (I did not create a site collection for this web app)
3. I have removed the content db of that new web app using Central Administration
4. I have run the stsadm.exe -o addcontentdb -url webapp-at-port-500 -databasename
5. Command is successfully completed, however when I check the Content Database page for that web app, it says that the Number of Sites is 0! Also, when I try to open http://webapp-at-port-500, I get the error saying that the webpage cannot be found.

Could anyone please help me, it's driving me crazy. Thanks.