Ok so I just recently got this imac 21.5 inch and it came with os x snow leopard I think it is, or the one that came before os x lion, and I recently installed os x lion, and ever since, this imac has seemed slower and choppy. If I want to go back to snow leopard should I just insert the software disc for the os x snow leopard, that came with my imac? Also is there any way to not lose my data without having to put it on a external hard drive or on a flash drive?