Everytime I open a document in SharePoint it asks:
You are about to open Name: xxxxxx From: xxxxxxx
How would you like to open this file? Read Only Edit
How do I disable this, so it opens directly into read only?
There's no simple way of doing that - Browser File Handling won't help you, because it is useful only when you want to prevent "Save document to disk" behavior.
Try to locate docicon.xml file and search there for one of your file extensions you want to open, and try to add there attribute OpenControl="". If that won't help, you will need to do some more customizations in aspx files probably with the DispEx method.
Check out the Browser File Handling section of this article. I think you'll want to set it to Permissive to automatically open the documents.