I lost all the originals, of the pictures I had. I can still view them in the library previews. Is there a way of making a jpeg from what is in the library?
Have you looked in the trash can?
If they are not there, you should restore your backups. (You do have backups, don't you?)
Next, you should try using an "undelete utility program" to see if you can recover your originals.
Last, you can use this Lightroom plug-in to obtain low resolution JPGs of your photos.
Jeffrey Friedl's Blog » Jeffrey’s “Extract Cached Image Previews” Lightroom Plugin
Retrieving data ...