Fuji Finepix A345 file size is too large. Can it be set to fix this?

If I take a picture with the quality set at 3:2, the average file size is almost 900 KB. If I then open the picture with Microsoft paint and then re-save it the file size goes to 180 KB. There appears to be no difference between the two pictures other than the file size. Is there a way to set the camera to do this so I don't have to convert all the pictures manually ? (and still maintain picture quality)