when you display an email, images are written to the system temp folder so they can be viewed. the file name used in reused, so if something is preventing the used file being removed, it will appear next time there is an image. Open the file manager/explorer in windows. Type %tmp% into the location bar and press enter. Select everything in the folder (use Ctrl +A to make it easy) and press delete Some files will be in use and windows will refuse to delete them, but a cleanup in this folder is something windows never does and it a primary reason windows systems tend to slow over time as this temporary data store grows out of control filling the local disk with old useless garbage