Taskbar not displaying properly in Windows 2000

[Haircut]

In Windows 2000 the taskbar only seems to display 5 things in it.
If I have, for example, six internet explorer windows open it only shows the first five in the taskbar and the last is nowhere to be seen.
I can still Alt-Tab to it, but the taskbar won't display more than five things.

Anyone have any ideas?

 

[ElDonAntonio]

Can you post a screenshot? maybe TweakUI can help you?