IE7 and Outlook Express are quite safe if you update the Windows OS with latest patches from time to time. This is important as Windows OS is very popular OS and there are many new security holes discovered from time to time.

Also don't forget to update the signature file on antivirus and anti-spyware softwares and scan you computer from time to time.

Here are more links to help you:

Securing Your Web Browser from CERT

Adjust your Outlook Express Security Settings

Hope helps..

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