I would first check in the bios what the current boot sequence is.
I can not tell from your description if you got the product like this (2nd hand perhaps), or if it suddenly started doing this. If the latter is the case, open up the latch and make sure the harddrive is still in it's slot properly. If that didn't help you, remove the harddrive and check if it works in another laptop. Only after these steps I'd consider another harddrive.