Whenever you double click on an attachment you get a message if you would like open or save the file. You would like to open it but you don’t want to answer this question again. There is an option which says “Always ask before opening this type of file” which you want to turn off but can’t since it is greyed out. you was able to turn this off on Windows XP but you cannot do this on Windows Vista.
Windows Vista or windows 7. Since that option is a system wide change and not limited to the logged on user, you must perform this with Administrator rights. Since everything is loaded as a user since Windows Vista and windows7, you must explicitly run Outlook as an administrator to change the option.
To do this follow below steps:
Hold SHIFT on your keyboard and right click on the Outlook shortcut after that choose Run as Administrator then press Continue or provide the log on credentials for an Administrator.
Now when you open the attachment you can deselect the option “Always ask before opening this type of file”.
Restart Outlook to have it run safely in user mode again.