Are you saying that the description shows the HTML tags around it when you try to display it?  The simplest thing to do is to call HttpUtility.HtmlDecode() on your description.  However, the whole point of encoding the HTML is so that you can avoid attacks through user input (specifically XSS attacks).  At the least you can call the InputFilter method off of a DotNetNuke.Security.PortalSecurity instance, passing in the PortalSecurity.FilterFlag.NoScripting flag.  Even better would be to use the AntiXss Library from Microsoft.

Hope it helps,