My JPEG photo has the 16 to 9 proportions of a widescreen TV or HD TV so How can I crop or print to fit a standard 4x6 or 5x7 or 8x10 frame without losing part of the picture?

Your image is proportioned 4:3. You can print it at 8" x 6" and then crop it to 7" x 5" but that is as close as you can get without distorting the image or matting the photo.

Alternately you could just take it to a frame shop and they will frame it at whatever size it is but that would cost more than an off-the-shelf frame. They could also mat the print for you i.e. you could give them an 8" x 6" image and they put it in a 10" x 8" frame and put a 1" white mat around the image. You could mat the photo yourself if you are good with crafts.