Need free software for making JPEGs of screenshots

Yes, a little bit of experimentation suggests that just using Print Screen key then pasting into Paint will work for me. Providing I then Save As to transfer the copy to a holding file using a suitable format for any future use with different software.

I suggest you try using the GIMP (GNU Image Manipulation Program). It is a powerful and free software which can be obtained on the site http://www.gimp.org.
Antonio.