Opening a mail, as far as I know, never requires a download. The mail just opens and you can read the body of the mail.
Downloading an attachment to your hard disk never requires a file association. It just copies the attachment to your hard disk.
Then, generally, you'd use a program to open the downloaded file. What program you need depends on the type of the file. For example, to open that swm file I discussed in my previous post, you need the program mentioned in http://filext.com/file-extension/SWM. But it could very well be that the file you want to open is of another type. If you can't open it, find the extension of the file you saved in Windows Explorer. Asking the sender how he made the file and what program he recommends to open it makes a lot of sense also.
More & more, when I open an e-mail,& it requires a dnld., I get this pop-up that tells me that there needs to be a file association for this particular dnld. -
HOW do I get this to work? - (Win 7, 64bit, 2yr. old Toshiba Laptop)