ConvIm

ConvIm is a lightweight and simple-to-use program which enables you to convert image files to other formats, such as JPG, TIFF and PNG, in batch mode.
This is a portable software, so installing ConvIm is not necessary. It means that you can place the tool on a removable device (like a USB flash drive), plug it into any computer and directly run its executable file. What's more important is that your Windows registry keys will remain intact.
The interface of the program is based on a standard window in which you can use the Explorer-based layout to locate and select images for processing. All you have to do is specify the output destination and extension, in order to proceed with the task.
Additionally, you can adjust the JPG quality, rotate, flip and resize pictures, enable ConvIm to keep the original extensions (to BMP only), swap the source and output folder, and more.
The simplistic image conversion tool takes up a very low amount of system resources (which can be barely noticed), quickly finishes a task and manages to keep a good image quality in the output files. No errors have occurred during our tests and ConvIm did not freeze or crash. We recommend ConvIm to all users who prefer a straightforward application.