The exact size, of course, depends on the playing time (in minutes and seconds), on how good the original compresses and the compression quality. 1 Mb a minute is a good approximation, in practice. I wouldn't trust 2 Gb to hold 1000 average downloaded songs. Just go for 4.
The causes of the Vietnam War were derived from the symptoms, components and consequences of the Cold War. The causes of the Vietnam War revolve around the simple belief held by America that communism was threatening to expand all over south-east Asia.
The Cold War was caused by the social climate and tension in Europe at the end of World War II and by the increasing power struggles between the Soviet Union [and the United States]. Economic separation between the Soviets and the west also heightened tensions, along with the threat of nuclear war.