If you use Outlook:
open Outlook:
1. Select Inbox
2. At the top select VIEW
3. Then if the preview pane is active, click on Preview and it will no longer be active
4. repeat for Auto Preview

If You use Outlook Express:
1. Open Outlook EXPRESS
2. Select Inbox
3. Next to the big buttons on top... Right click and choose Customize...
4. In the left hand pane of the window that comes up ... find and select Preview..
Then select Add... Then close.
This will put another big button on the menu at the top that you need to click on to stop OE from previewing e-mails as they are highlighted
5. DO NOT OPEN Any e-mail that you are not expecting that has an attachment!
6. OE6 Read emails as Plain text: Tools->Options->Read
7. OE6 Disable/Enable attatchments from being accessed: Tools->Options->Security

Also go to Tools, Options, Security Tab,
Make sure you have Security Zone set to Restricted Sites