Hey guys. There are a few entries here requiring solutions to do the opposite of this, and others vaguely related. In one of them, the poster asked how to do this on Mozilla Fir
The obvious answer is to open the link with target="_blank". As you said, Firefox and Chrome will open a new tab.
Regarding IE - the behavior is up to browser preferences. By default (in IE7+ obviously) I believe the behavior is defined as open new tab. If the user decided the behavior should be a new window, there's only so much you can do about it.