Open your .BMP image in Paint.NET, Photoshop, GIMP or any other “paint” program that can handle transparency and such.
Remove the background if there is one.
Save As - > .PNG
You can only use .PNG in an engine using DX8, and .BMP in the DX7 engines. They aren’t interchangeable.
It seems like that you are in trouble of iamge processing.
I’m a green hand on this field, too.
However, a friend told me to try free trials of some professional image processing tools first.
Youcan also have a try.
BTW, an image converter which can help you solve your problem is also offered by them.
Hope it helps.
Also, Arronlee, please don’t give out useless information and especially not links for things with no bearing on the issue; I imagine you are in some way affiliated with the software, and thus it is in your interest to have people use it? Please don’t be silly.
That program is not helpful here because, I imagine, it won’t be able to remove the background, so is useless.