If your friend has installed a program for stopping pop-ups, it may prevent all new windows from being opened, even when a link is clicked. I installed Pop-up Stopper (I think that was the name) and it was necessary to hold down the CTRL key when clicking on a link to open up a new page.

Ask your friend if he installed any pop-up blocking software. If he doesn't remember, or shares his computer with others who might have, look at the icons that appear in the system tray by the clock on the taskbar when his browser is open. A pop-up blocker might not include a system tray icon, though, so if there is nothing there, I would look under Start>Programs, the Add/Remove Programs Control Panel, and finally in the Program Files directory.

Ad-Aware wouldn't look for programs that are intentionally installed. Hope it is this simple.