IE7 Pro already does this.
IE7 Pro has something called Tab History, and it show a long list of tabs before they were closed. It offers up to the last 15 tabs.
I suggest anybody with IE7 download IE7 Pro. IE7 Pro offers a lot of IE7 enhancement add-ons all in one package. It's very convenient and I haven't noticed anything bad happen with it.
http://ie7pro.com/<</a>/P>