Bitmap files (extension ".bmp") are quite space consuming. I suggest you convert them into ".jpg" files with "Paint" (programs - accessories) or "Corel Photo Paint".
The resulting files will be smaller, which means they will use less memory and disk, and load quicker.
In any of the above mentioned tools:
- Open the .bmp file
- Select the file
- Save As: choose the .jpg file extension explicitly
Your file is now considerably smaller in size and can be read/edited by other appropriate software, for instance Microsoft Photo Editor.