Develop software that runs on Windows 8. Will be connected to an IMAP server and look for new mail. When mail comes in, it will see if there is an attachment. If there is, it will save the attachment into a folder based on the username in the email address. For example, if the email is sent to you will save this to a folder called "xyz\abc" - this is parent folder xyz and subfolder abc. If it's you would save in "xyz\abc\123". If it's you would save in "xyz". Then, mark the file as read and archive the email. Auto-check for new emails every minute. If the folder doesn't exist on the PC, then create it.
Have some error handling in place so that the software always runs without having an issue. To confirm that there are no issues, send an email to every hour that says "Email attachment software running ok".