How can I convert my chess diagrams from pgn to jpeg or giff file format?

Answer 1

i open all my png files with irfanview

if you don't want to download anything you could try opening your png files in Paint. and the doing a file/save as...

Answer 2

If your program does not support screen output, you can try screen capture program.

I use faststone capture program.

You can download the program from their website.

http://www.faststone.org/