Convert mbm to dds Online: mbm2dds

You can use Tom's Editor to easily convert images from
Psion Series 5 Bitmap .MBM to Direct Show Surface .DDS.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

MBM

Psion Series 5 Bitmap is an image format with extension MBM.

DDS

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.