Clean nicotine laptop?

How can I rid my old laptop of the yellow brown sticky dust? With compressed air it goes Schimmels ned

You can try it with isopropanol or alcohol. Drizzle a little on a kitchen roll and work the affected areas with the cloth.

I've only seen your fan image now. Would recommend an old toothbrush and isopropanol. You can remove the mud that you remove with a vacuum cleaner afterwards.