If you have Windows XP, open the picture file with Microsoft Photo Editor and click on 'Image' 'Resize'. Change the units box to Pixels and change the values until either the width or height is about 500. Save the file and it should be below 100k. If not repeat the resize making the pic smaller until it is.
If you have another operating system, there is free or cheap photo editing floating about on the net.
If you have a digital camera or scanner, there may be photo editing software included on it.
Good luck.