Microsoft Outlook 98 & 2000
Open the message in a separate window (double click)
Under the View menu select Options
Copy the text in the Internet Headers window (unfortunately it doesn't include the message itself).
Paste into the Headers and Message box on the the form page.
Close the options window
If the spam header shows "text/html"
Right click on the body of the spam, and choose 'View Source'.
This automatically opens the HTML code up in Notepad.
Copy the entire message body.
Paste into the form.
Make sure to leave a blank line between the headers and the message body