I’ve written about this problem a few times over the last few months: when you open an attachment on an open email by double clicking on it, the attachment is always read-only in Outlook 2010. In previous versions of Outlook it was editable and if you did it correctly, you could edit the attachment and save the changes back to the email message. People who are used to doing this are annoyed by the change in behavior in Outlook 2010.
Anyone who receives an email with images attached will be unable to rotate the image in an image viewer. A workaround for those using Photo Viewer exists: in Photo viewer, click on File, Properties, General tab then clear the Read only check. Repeat for each image.
The read only attribute can’t be changed for Word and Excel documents, however an annoyed user created a VBA module which replaces this functionality, though not nearly as seamlessly as his users are used to. For links to the download and instructions, see:
Do you edit and save attachment back to an email message? Solution by Krazycure