Contouring Large Area

I was wondering what the best procedure would be for contouring a large geographic area? My objective is to create 20m contours covering the Arabian Peninsula using GDEM30 data. I have smoothed out the DEM which has created a 50 gigabyte 32 bit file. When I try and generate contours I get an out of memory error. Even when I try and generate 1000 m contours I get the same error. Do I need to convert the image to 16 bit? Do I need to tile the image into smaller sections? If so, what size would they need to be? If I generate multiple contour files, how do I combine them all back together?

Thanks in advance

Bruce Burwell
GIS Analyst
Saudi Aramco