Security tips blog, security-hacks, has posted details on how to enable DEP for Internet Explorer 7 in Vista.
“By default, DEP is turned off for Internet Explorer in Vista. If DEP is so powerful, why is it disabled for important applications such as Internet Explorer? Well, the answer is simple. Microsoft disabled DEP to maintain backward compatability with other plug-ins and add-ons that simply do not work with DEP,” read more on Security-Hacks.com