I have a late 2008 24 inch iMac. Last year I upgraded to double the ram from 2gb to 4gb. I think this messed up the computer after 8 months. I just took reinstalled the original ram and it's working now. Before all that would happen is it would take forever to start up and then just keep loading. This has been fixed but now when I dump stuff in the trash nothing shows up. I go to the trash and it has a ?? mark. Do I need to get a new HD or just update/full reboot the system. I lost the original install disk. If I download the latest OS can I reboot to factory settings?