new link opens in IE7 instead of tab

I noticed yesterday that when I click on a link for example a message comes, and it opens a new IE page. Before, it was a tab that used to open. How do I revert it back ,ie, click link = tab?
Thank you

And if you click once on the wheel of your mouse, it does not open a tab?

How do I go about making all external URLs to open in
a new tab in IE7 instead of a new window?

Or at least open a new tab programmatically from .Net?

At the moment I have:
Process launchprocess = new Process();launchprocess.StartInfo.FileName = m_currentItem.Link;launchprocess.StartInfo.Verb = "open";launchprocess.Start();Strangely this always produces a new tab on my home machine, but still produces a new window on my work machine.

Strangely this always produces a new tab on my home machine, but still produces a new window on my work machine.

If you are talking about hyperlinks in this form:

<A HREF="newwindow.html" TARGET="_blank">a new window</A>

that normally pop up a new browser window, you can change that behavior to opening a new tab in IE7 as follows:

Tools\Internet Options\General\Tabs\Settings\When a pop-up is encountered\Always open pop-ups in a new tab