As you know what is virus and its functions. If you want to avoid download a file that may have virus attachment then do following steps:
Open run and type in run (gpedit.msc) without round braces it will open a local group policy now click on user configuration then click on administrative templates after this click on windows components after this double click on windows explorer.
Now double click on “Configure Outlook Express” in the right panel of local group policy. It will open a new window there are three options you will have to click on enable radio button and from options mark check box that say “ block attachments that could contain a virus” after that click on OK button.
Close the global policy editor which is previously opened through gpedit.msc. If you do this then you are free from virus which is attached to any file which you want to download.