I have a imac 20/2.16/1g/250/sd/ap/bt purchased may 2007. My operating system is mac osx snow leopard--v 10.6.8. I was recently notified by apple that this is not supported any more. I can't even upgrade to the current os. It is very, very slow and the rainbow wheel spends a lot of time spinning. Is this because my computer is old? Would a new one be faster or do i have something else wrong?