Hi, all. I bought this from Ebay: Apple MacBook Core2Duo Unibody 2.4GHz 4GB 250GB 13" MB467LL/A Says it comes with Leopard installed. Question is should I upgrade to the latest OS the machine can handle? I'm mainly wondering if upgrading to a newer OS will slow performance since presumably a newer OS will need to use more resources. All we're going to do with the computer is use it for Internet stuff, word processing, and the occasional DVD. Thanks for the input.