XnView


totally replaces ACDSee screenshots

XnView is a picture viewer and converter. It supports over 400 image formats, so it is very unlikely that you will come across a picture that you cannot open. It also has some basic editing options, such as rotate, crop, brightness, contrast, filters, effects, and more. It can also rename and convert images in batch. I personally think this program is better than IrfanView, which is another freeware picture viewer.
or try IrfanView