If you see a message right at the start of the boot-up process on the lines of "No system disk" then disconnect any external hard drives and USB sticks and make sure the CD/DVD drive is empty as the computer may be trying to boot from something other than the hard disk. If that doesn't help, restart and press the key (usually the Del key or one of the F keys) to get into the BIOS settings and check that the boot sequence includes the hard drive - the settings might have got corrupted.
If you're sure that the PC is trying to boot from the hard drive then a common reason for failure is corruption of the partition table. There is rarely any need to use data recovery software in this case. All you need to do is fix the partition table and your files will reappear as if by magic. A good and easy to use tool that can do this for you is the Partition Table Doctor Boot CD.
The Partition Table Doctor Boot CD is available online as an .ISO CD image that you can download and burn to CD using any CD image burning program. After you have done that, boot the PC from this CD. In most cases, Partition Table Doctor will detect the problem automatically and guide you through the steps needed to fix it.
- See Tech-Pro.net's review of Partition Table Doctor Boot CD