Yeah, that's why I said, "All of it". If you have to ask, you don't have enough. The more you have, the better it will run, at least up to about 8GB, after that you might not notice an improvement. This is just the way OS are ever since the mid 90s and the advent of swap discs. Before swap discs it was easier...the OS would just tell you to f*ck off and buy more RAM!