I can only re-iterate the previous answer. However if the laptop is currently working you can run disk diagnostics on the drive which could save your life. Use the windows supplied disk tools. Open my computer, right click on your drive and select properties, tools, and select 'check now' this will check the disk for errors. It will require a reboot as you cannot run it interactively. If your drive does finally give up and you don't have a backup then expensive data recovery will be your only option. Do it now before its too late!
Re-installing the OS from the original disks will return it to the default Windows but if your drive is dying it won't solve the problem.
John
hzplj9, July 2009