Hi Rob,
If you have a Windows pc, it should have Microsoft Paint installed. Copy your original image file, open the copy. From the File menu, select Save As. Select jpeg, and if you can see advanced options, see if you can set the compression rate a little lower (30-40 range). That should do the trick already. If you can't see a setting for the compression rate on the Save As dialog, you might try the Properties section, available from the File menu.