The hard drive may be starting to fail or has already failed, so you need to test it to be sure, using the drive manufacturer's Diagnostic Software for DOS
. The links are here: http://www.tacktech.com/display.cfm?ttid=287
Create a bootable CD from the diagnostic software's ISO file using IMGBurn
on a working PC:http://www.filehippo.com/download_imgburn/
Boot your faulty computer or laptop from that CD and the diagnostic program will eventually open.
Test the drive with the Long/Extended test.