Since I had not heard of "Explorer 11", I had to go looking. It is very important when using the word "Explorer" that it be used correctly and completely:
These are the computer related "Explorers" I found:
There is a
Windows Explorer
Internet Explorer (currently v6,7,8)
These are part of the OS.
Downloadable "Explorer" programs are
Process Explorer
MSN Explorer
Under "Explorer 11", I found these:
Internet Explorer 11 with several versions of EaseSoft Barcode ActiveX Control
http://www.topshareware.com/internet-explorer-11/downloads/1.htm
Process Explorer 11:04
Intentia Movex Explorer 11.x
Since the Taskbar is a part of the OS and not IE-as far as I know- reinstalling IE won't help.
My best guess is that the problem has something to do with either the download or configuration of whatever "Explorer" you downloaded and I would suggest you uninstall it and assess the Taskbar after.
I want to make sure that you realize you can not only move the Taskbar around but also reduce the height of it by placing the cursor on the top line of the Taskbar and while holding the left mouse button down, 'pull' the Taskbar downward so as to make it the height you want. (no offense intended here, but some people actually don't realize this can be done!)
One other thought. I have seen some systems with so many added Toolbars on the Taskbar, that the Taskbar HAS to re-size itself in order to accomadate them.