A filter to delete all messages with a .rar, .zip, .scr, .exe, .pif or .vbs extension on the attachements for example sould do the trick. Of course outlook would still have to read through the message text to use that filter, even if it doesnt display it.
You can also hold down CTRL and select the messages you want to delete and hit delete on your keyboard. However, if you're worried about virii, then I highly recommend you ditch Outlook immediately. Its nothing more than a security risk.
agreed, i just recently switched to mozilla thunderbird. it's a very good replacement for outlook (ie: you won't have any trouble using it if you are used to outlook)
in the meantime you can disable the preview plane like others have said. on individual emails use properties - "view full headers" to view the email safely.