I read this article today – IE9 Tabs instead of New Windows for CRM 2011, I have had a few users of CRM who have complained about the number of windows they can soon have up on their screen, sometimes you can easily get 8 screens open and then you spend ages opening all the screens trying to find the one you want.
The blog linked shows you how to set pop ups to tabs in IE9 but after reading the instructions it seemed the key to stopping CRM creating lots of new screens was stopping the pop screens. These settings can be also be set in IE8 as you can see below.
I am going to give it a go for a while to see if tabs are better than pop ups