Hi alfrae, I think this is what should happen in Windows 7:

When you "minimize" a window, the window should stay just as you left it, all tabs still there, all pages still in their tabs. Then if you mouse over the Firefox button/tab on the Windows 7 Task Bar, you should see a preview of all your Firefox windows and be able to switch to them. If the preview feature is disabled, hovering over the button/tab should display a list of all your open Firefox windows.

Where does this seem to be breaking down? Are the windows closing instead of minimizing, or is Windows not listing all the windows you actually have open?

If a window seems to have closed, you may be able to open it from the History menu in another Firefox window.

History > Recently Closed Windows

By default, Firefox only remembers a few closed windows, but you can expand the number.

If Firefox doesn't think the window was closed but Windows does not show it, hmmm, maybe there's a problem with the interaction between Firefox and Windows.

By the way, when you said "when I open another web page", what method are you using to open it? Are you opening a new Firefox window to your home page, or clicking a link in another program (e.g., Adobe Reader, email program), or using a desktop shortcut, et cetera?

If you open a new page then that page may open a new tab in the same window and that would explain the disappearance of that window. You should then have more tabs in that window or in case this page got opened in the same tab then the current tab should have tab History on its toolbar Back and Forward buttons on the Navigation Toolbar.