The only way you''re going to be able to do this without bringing your computer to it''s knees is as (I forget who) said above - do your map in sections, then work on each section seperately. You''ll end up having to write a map-merger but (since you''re going to have to write an image-to-tile converter and some kind of attribute-layer editor) this isn''t as big as deal as it could be. Then just stream chunks of the map in and cache ''em as needed (yes, anything faster than an ancient IDE drive on a 486 should be plenty capable of bringing in decent sized chunks of your map in a timely fashion). You''ll need to do a little memory-management work and tile-caching work but that''s kind of a foregone conclusion with the approach you''re taking.

It''s not rocket science, it''s just a lot of grovelling in code to get it all working. IMNSHO...