Just for the record: PNG uses a lossless compression formula (effectively the same method used to compress ZIP archives) and so will always give a true image, unlike JPEG, but will generally produce much larger file than a JPEG.
There is very little advantage in converting PNG to GIF; the PNG will normally be 10%-30% smaller than the GIF and the format has other advantages too.
The only real reason for using a GIF these days is for animated images... or if you need to support some ancient browser for some reason.
Also for the record: if you have Word 2007 you can extract images directly by unzipping the docx file and looking for the PNG files. A docx file
is a zip file. Simply rename <file>.docx to <file>.zip and you will be able to open it with WinZip or similar. You will find that it contains a separate .png file for each image in the document. The only problem is working out which file is which image