Question about Outlook Express

Both gingerandbuddy and Tuscoro have described exactly the problem I have encountered with attachments (all attachments).  Everything was working fine with Windows Mail until a week or so ago when suddenly attachments wouldn't open. One of the suggestions I read somewhere was to switch to Windows Live Mail, which I did after a lengthy download time. The problem persists, however, except that I can now print PDF files directly (a new option in Windows Live Mail) but I still can't open or save them. I have also received the message that some very reliable software I was attempting to download contains a virus (which I don't believe) and the download was automatically deleted. I have Windows Vista, IE9, and McAfee Security Scan. I have done a complete scan for viruses with none found. My service provider is the local cable company which is a part of a major telecommunications group. I think the problem must have started when one of the automatic updates was installed on my computer in the background and the other users seem to be of the same opinion. None of the answers provided to them solve the problem.  It is serious for me because I receive much important information via attachments. Help is needed urgently --- perhaps we should revert to an older version of Windows Vista, but how can that be done? 

original title: Attachments cannot be opened or saved