Click Start, Run and enter REGEDIT.
Go to:
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Toolbar
(if the Toolbar key doesn't exist, right-click on the Internet Explorer key,
and choose New > Key, and name it Toolbar).
Click on the Toolbar key in the left frame so that it shows the contents in
the right frame.
If there isn't a string called BackBitmap, create one by right-clicking on a
blank area in the right pane, and choose New > String Value, and name it
BackBitmap.
For the 'Value data', type in the path that points to a BMP file which you
would like to use as your Toolbar Wallpaper. (i.e. C:\Windows\example.bmp or
C:\My Documents\sample.bmp)
If you'd like Toolbar Wallpaper only on Internet Explorer 5 windows create a
string called BackBitmapIE5 instead of BackBitmap.
*Note - This tip also works with IE5.5 and IE6. Regardless of your IE
version (IE5 or higher), you would still name the string BackBitmapIE5 if
you want to apply Toolbar Wallpaper only to Internet Explorer windows.