Hey mwny. Although this could be an HDD related issue there might be other things causing this, such as power failure. Does it not start up at all or it enters a boot loop of some sort? Would you please give a bit more specific information on the issue? One of the ways to isolate the problem and see if it's the hard drive, is to connect it to another computer and run the manufacturer's diagnostic tool to test the HDD.
Hope that helps.