Install on Demand?

I have suddenly been getting email from my two Yahoogroups lists that causes outlook express to pop up a message box called Internet Explorer Install on Demand. The box says I need to download a file in order to read the characters contained in the email.

The latest such email was from Ben Fleming on this list. The message box contains a check box next to the phrase "never download files of this type" but it will not let me put a check in the box. The other thing peculiar is that after I click it's cancel button the box dissapears and the email shows up with no unreadable characters apparent.

Is this a virus (Ben, you digitally promiscuous person you!), is it some spyware Microsoft wants me to download, or is it legitimate? I've used the same outlook express for two years without seeing this message. I have IE Explorer blocked by the firewall and never use it other than to view jpegs off line. Seems outlook express managed to acquire this feature on it's own just recently.

Doug


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