Thanks Viper.Originally posted by Viper Zero
When IE saves pictures as bitmaps, it is because IE has no more space on the hard drive to save it (a copy of the bitmap) as a jpeg (or other file type) and just pulls the image (the original bitmap) from the cache.
Go to Tools > Internet Options > Click on Delete Files under Temp Internet Files.
http://support.microsoft.com/?kbid=260650