The hard drive has probably failed and needs replacing. You can test whether or not it has failed by using the drive manufacturer's diagnostic software for DOS which loads from a bootable CD. The links are here: http://www.tacktech.com/display.cfm?ttid=287
The diagnostic software for DOS is downloaded as an ISO CD-image file.
You can create a CD from this file by using IMGBurn: http://www.filehippo.com/download_imgburn/
When you've made the CD on a working PC or laptop, boot your faulty laptop from it and the diagnostic software will load.
You may have to go into the BIOS Setup
first to set your CD drive as the first boot device.