i left my eMac in my car for a few hours in cold weather. after bringing it home and setting it back up, turning it on only yields the grey loading screen with the 'apple' logo. the 'loading' graphic runs continuously and the startup process does not seem to actually begin [save for one time when startup completed but brought up a half-sized non-functional interface]. how can i begin to pinpoint the nature of the problem? is there a system diagnostics i can run from a special startup? im trying to find the OS installer to boot.