If you need to use Rules to create a new user after a condition, follow this simple tutorial.
Before you begin:
It is helpful to turn on Debug rule evaluation to see if and where your rule runs into issues (Rules > Settings > Debug rule evaluation).
Always use a valid e-mail address, otherwise a new user will not be created.
Create a new rule:
- Navigate to 'Add a new rule' (Rules > Triggered rules > Add a new rule).
- Create a Label for your new rule.
- Select the event on which you want to evaluate this rule.
- With the action to create a new user, define a username, for example, you can use [node:title] for it and [cck:email-raw] for e-mail (this case is a after-save-node-type with cck field for this e-mail).
Then, the problem is: you can't generate a dull password.
So you need to specify a "send e-mail to user" action at the end and then there at the textarea you use [newuser:password] (check your token replacement value). Or you create a non-variable password, as "admin" (obviously not secure).
You can also add a role to this newly created user.
If you want to avoid using duplicate e-mail addresses, one way to avoid this is to use http://drupal.org/project/unique_field which disallows duplicates of a CCK email field.