When Emails have a virus they are usually stored in the form of an attachment as far as I know. My question then is the following, do you need to open the attachment for the virus to start spreading, or does it do so as soon as the email is opened? On Outlook express for instance, you cannot click on an email without the email opening up. Just something that is bugging me.
As long as you do not open the attachment you "should" be safe. However, I would still recommend frequent virus scans. You should be ok though. Especially since recent versions of Windows request your permission for any kinds of installations. This is just for this kind of scenario, that unwanted installations can be prevented.
The best advice I can give you is never to open up EXE files. Even word documents however can carry viruses. If you have recieved an email with a file attachment, make sure that you scan the attachment first before opening it!