I don't know why your file is taking up so much room. I just did a series of tests (using the image of a tune which I displayed at 100%, & which took up about three-quarters of an ABC2Win page), & got the following results:
GIF (cut & pasted into either Paint or Paint Shop Pro): 13kb
(did you switch the interlace option off?)
JPG (Paint Shop Pro, lowest compression/highest quality: 118kb
JPG (Paint Shop Pro, highest compression/lowest quality: 19kb
JPG (Paint): 80kb
BMP (Paint Shop Pro): 1.7mb
BMP (Paint): 2.5mb
Monochrome BMP (Paint): 106kb
If you have any other graphics packages, you can copy the bitmap into it in the same way as you would into Paint, & then save it off in a different format.
Line Breaks <br> added.