How do I make the taskbar smaller? Or larger?

Description:

I'll assume that "strip", as you call it, is the Windows Taskbar.
Most folks don't realize that it's really just a special window, of sorts. And as a window you can resize it and even move it.
Sometimes people are surprised when that happens by accident.

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I'll use Windows XP for my example here, but the instructions apply to Vista and 7 as well.

Am I Locked or Not?

Have a look at these two task bars:

The difference is slight, but important. The upper taskbar is unlocked. You can tell because dividers between the taskbar sections are present, and the top of the taskbar is a little thicker:

The difference is simple: when locked you can't make changes to the taskbar layout, size or position. So, our first step is to unlock it:

Right click on an empty area of the taskbar and you'll get the pop-up menu you see above. Click on Lock the Taskbar to make sure it's unchecked.

Size Matters

Resizing the taskbar is now pretty much like any other window, except that the resize will happen in steps.
Hover your mouse over the top edge of the taskbar - the edge that was added when you unlocked it:

As you can see the mouse pointer has turned into a double arrow, indicating that what's underneath is resizeable.
Left click the mouse and hold the mouse button down. Drag the mouse up, and the taskbar will, once your mouse reaches high enough, jump to double the size:

You can go even larger if you like.
And of course the reverse it also true: if your task bar is too high you can make is smaller as well. In fact, you can make it so small as to be nearly unseen:

You can hover over what's visible if you like and resize the task bar up to its normal size.

Location, Location, Location

We normally think about the taskbar being along the bottom - but it doesn't have to be so. Particularly on wide screens you might prefer to have it on the left:

Or the right, or the top. Just click and hold on any empty area in the taskbar while it's unlocked, and drag it to the side of the screen you'd like it to be on.

Lock'er Down

Finally, when you have the taskbar where you want it, and the size you want it, be sure to right click on it and make sure that Lock the taskbar is checked.
Based on what I hear it's fairly common that the taskbar ends up getting unexpectedly resized or moved. Locking the taskbar simply prevents that from happening.