Since you say your black hole is "right next to the Start button" assume you're talking about the main bar that's usually at the bottom of the screen. If you right click on a blank spot on the toolbar, you should get a menu for toolbar management. (You might have to right click in the black hole - that's something I've never seen?)

If you click "Properties" on the menu that comes up, you should get a new little window labelled "Taskbar and Start Menu Properties." I don't have an XP to look at, but in my Win7 on the Taskbar Tab there's a "Taskbar Buttons" that's normally set to "Never Combine" but the dropdown offers "Always Combine" or "Combine When Taskbar is Full."

While it's only a guess - it sounds like you've "collapsed" all your buttons into one (black) button hole.

As indicated, I don't have an XP handy, and things may have changed, but I suspect that the "right click a blank spot" on the toolbar may get you to a menu that will help if you poke enough things on it. (But it's only a guess.)

If you haven't tried it, a "reboot" sometimes helps - but nobody really knows why.

John