Question about file association and opening method in Win 7

Because the work needs to analyze the source of a message, etc., because I am used to using Office Outook to view the mail attribute information, and the current system default mail program is Windows Live Mail, so use "Open with" to specify the opening of the mail by Office Outlook, but the opening method is specified because of negligence, did not remove "Always use the selected program to open this file", the results of the check can be imagined .

After this operation is executed, Office Outlook does not open the correct mail file (.eml type) correctly. Now it can only restore the previous state first, according to the experience of using Windows XP in the past. File key and open mode can be set in the folder option, but gOxiA is lost under Windows 7! I haven't found it for a long time, because it is the reason of the RC version. It is difficult to search for relevant information in the help system. At least through several keywords, I can't search for related help windows7 system download. But I am sure that the system will have a place to set up, which reminds me of the control panel