I have a 24" white intel core2 duo iMac. Lately, it's been very sluggish. The hard drive is hardly full (306.15GB left out of 460GB). On avg it takes about 30 seconds for it to boot up and another 30 or so for iChat/Gmail notifier to launch on start. There was a time when it only took about 30 seconds for booting up and the launch of those startup apps. Also, earlier today it had difficulties coming out of the screen saver and my entire screen was pink and pixelated. Should I be concerned about my iMac? Should I reinstall leopard and restore everything with my time machine backup?