Access 2007 transparency images loaded from attachment field

I need to place transparency images onto my ribbon in Access 2007 I have setup an attachment field in an access 12 table. I have added some images with transparency backgrounds of the .png format. Using the code supplied by microsoft the .png picture format is not recognised however .jpg and .bmp are loaded up ok. Has anyone had any success with loading .png using this method? If so how did you do it?