Often you will have pictures in one format and want to explore using it in a different manner.
Built into Office 2003/7/10 is a mini app called Microsoft Office Picture Manager.
1. Go to Start > All Programs > Microsoft Office > Microsoft Office Tools > Microsoft Office Picture Manager
2. Browse to the images you want to convert and select them
3. Go to File > Export
4. Under Export with this file format, click the dropdown and select one of the formats (TIFF, PNG, JPG, BMP. . .)