problem while downloading html attachment.

Hi,
I have an application in which I have to upload and download files.
while downloading all attachments are opening in its own file type.
But html attachment is opening in in the same window.
I declared target="-blank" but here iam seeing a new IE window and then promting to Save or Open or Cancel.
My requirement is it should not open any IE window but prompt message and then opening it in another IE window.
Please get me out of this issue.

Here is the code:
 <asp:HyperLink ID="hLnkFileName" runat="server" NavigateUrl='<%# Eval("FileID", "~/Documents/OpenFile.aspx?FileID={0}") %>'
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