The folder with the flashing question mark means the machine can’t find a boot drive. Sounds like you may have a hard drive failure. I hope you have your critical files backed up. I’d try booting off your OS X install disk and try running Disk Utility and repairing the drive or some other tool like Disk Warrior on it. You may or may not be able to salvage it. If you are able to get the drive back up be sure to copy all your important stuff off of it. Good Luck!!!