I have a Macbook Pro OS X 10.4.11. It's about 3 and 1/2 years old. The last few months I have not been notified of any software updates like there used to be regularly. When I manually "check for updates" it says none are available. Looking in the history of updates, the last one I received was last fall. Why is this? Software is too old? My Apple Care has expired? And how do I solve it? Do I have to buy a new version of OS X? Thanks in advance!