It depends on what e-mail client you are using. Outlook 2003 does not automatically download any web content by default and further protects you when it moves items to the Junk email folder by converting it to plain text. If your mail client has tagged it as junk then it should have made it safe. DO NOT click on any links in potentially junk emails.
If in doubt, delete it. If it was important from someone you know, they will call you if they don't get a reply.