Heya. That youtube video has some incorrect information and you should follow this guide instead:
https://kangworlds.net/tutorials/cmp.htmlFor this error specifically, there are two workarounds:
A. Use an older version of Windows. compimg.ovl is a
16-bit overlay library so depending on the system it may fail to hook into the 32-bit main process. Also make sure that your version of COMPIMG actually came with the OVL, if it didn't, I can provide you with the file you need.
B. Ensure the BMP file is the correct color format (BMP version 3, 8-bit color). This will bypass compimg.ovl entirely. It will only run if it needs to convert the image format before compression.