I use IrfanView for several reasons:
- It’s fast and easy to use
- It’s free
- It can convert very easily between different graphical formats
- It can add a nice border to an image
- It can decrease the number of colors for an image
(which significantly reduces the size, with no visible loss in quality)
- It can create negatives from an image
- It can batch convert/rename
(for instance, I can convert in one step 100 bmp to png, with resizing)
- It can crop very precisely an image
Here are the download links:
IrfanView :
http://www.irfanview.com/main_download_engl.htm
The PlugIns (are also free)
http://www.irfanview.com/plugins.htm
With plugins you can do some extra stuff, like opening a PDF file.