Convert esm to dds Online: esm2dds
You can use Tom's Editor to easily convert images from
Enhanced Simplex .ESM to Direct Show Surface
Tom's Editor is a free, online image manipulation and converter program.
Go to Tom's Editor
Enhanced Simplex is an image format with extension ESM.
DDS are files invented by Microsoft to be used in games, mostly as textures. Images can be compressed to save space but the compression methods defined by DDS are all very fast in terms of coding and decoding.