I have made a new content type called wall and used user reference on it. Is there a way to auto create node whenever a new user is registered? I found the Autocreate Node Reference module but it doesn't have version 7 so I'm looking for an alternative.
This is a good example where Rules module can help you. I myself probably just write some custom code, since that's easy for me. But if you don't want to/can't do this, Rules can help you.
You can setup a rule, that is executed when a new user is created that will create a content of the chosen type. With tokens you can populate the values needed.
Using Rules can be a bit complex, but it's very powerful.
There is the Node Reference Create module for Drupal 7 (and 6) which does this. But probably you need to write a custom module to create a node after a user has registered.
In addition to what googletorp mentioned, do you think the link below would be of any help?