Go into your setup (CMOS) and check to see if your settings are correct it sounds to me like your setup needs configuring. If that is not the problem you have probably had a head crash. If you rebooted before you hard disk stopped spinning you could have damaged your hard drive. I used to be bad about that myself. When you power down your hard drive you need to wait at least a minute before rebooting. If you don't you tork your platters on your hard drive which leads to deterioration of your hard drive. As far as the cdrom you might not be loading a driver for DOS.
Stay alert, stay alive!