Non standard BMP file

[JJ]

The following is a BMP file that is an image map. I want to modify it.

http://healthcaresales.com/graphic/imagemap.bmp

The file wont open in many of my graphic apps (MS Paint, MS Photo Viewer,
MS Photo Editor) and reports unknown type. If I open it in a web browser
there is "tearing" along the edges. I wouldn't edit it these programs of ,
but it does show that there is something non-standard about the file.

It does open in PhotoShop (upside down). If I open the file and change any
part of it and then save it back other parts of the image are distorted and
destroyed.

It obviously is a non standard format BMP (I tried also renaming it to RLE).

Any idea what program I could use to edit it? I need to keep it in the
original format as I will put it back into the original program to use as an
image map. Also just curious about the format in general and what is
happening internally (on a very basic level).

Thanks