If it's getting stuck in POST, then something is pretty heavily hosed. If it were a desktop, I'd consider resetting the BIOS settings (you know, pull the battery from the motherboard). Otherwise you may have a bad motherboard, bad memory, heat-damaged CPU, etc, etc.
If it's getting just past the POST, but not booting the OS, then you may have a bad or corrupted hard drive. If it's just corrupted, reinstalling Windows should work. If the drive is bad, you need a replacement.