Sad Macintosh Error displays at startup

Hi,

I have a old Macintosh pc. From few days, a square box's comes, everything slows down and eventually fails, then displays the Sad Macintosh. What does this mean ??? Do you have any idea ????

Use Disk First Aid to see if there is a problem in the internal hard disk directory. To do this, Simply launch First Aid, highlight the icon of the hard drive that matches and click Verify. (In previous versions of First Aid, you must click Disk until the unit selected is the internal hard disk and then click Open and Start.) If First Aid is a problem that can not repair, you may prove of some use third-party disk to correct it. If, despite all attempts, not repair the disk, you need to reformat. Make sure you have a backup of the data contained in the disk before beginning this process. In the event of not having made any backup, can lead the drive to a service engineer in recovering data from hard disks data.

You need to Reset PRAM - hold down the Command-Option-PR during startup to update the port information, devices, Finder, and network settings. If the computer starts after resetting PRAM, it is likely that the parameter RAM contains corrupt information.

Perform a clean installation. - Follow the steps in the TIL or volume 1 of 1 of the "Information Alley" to perform a clean installation of system software. If the computer starts after carrying out a clean install is probably one of the files added to the System Folder or one of the old system files were corrupt. Look carefully at the Storage folder created during the installation process from scratch and look for fonts, extensions and control panels you need and place them back in their proper location.

Reformat the drive and reinstall the last backup. Contact vendors of hardware or software that uses third party. If the computer starts After these attempts, has managed to correct the problem and the system is ready for operation.If the computer still does not start, it is likely that there is any problem with the hardware.

Booting from eldisco Utilities - Restart the computer booting from the Disk Tools floppy disk. If the computer reboots from the floppy disk, it is possible that the system software is corrupt or there is some problem with the hard drive. Check the version number of the conflicting item or items to ensure they are compatible. Try reinstalling the extensions from the original diskettes or contact the software vendor.