i think most magazines will recomend you to use 300dpi..but when it comes to B&W, they have different kind of requirements, the best way is to ask the publisher~

i've actually came across a magazine that requires 150dpi, it's called wall street journal, was doing the magazine ad for adidas golf~which somehow the magazine have lotsa requirements to it..not only the dpi, also the gray scale where it cannot exceed how many percent of grayscale...a fuss~

yeah...even by using a 3Gig proc and i.5GB of ram...my pc still slows down after opening the files...maybe shud try dual proc..hahaha