|Back up immediately.|
If under warranty then bring it in for free service, if not then call the manufacturer's tech support and get a full recovery disk set for your machine in order to reinstall your operating system, drivers, and included software (many of which you will eventually uninstall), usually for a small fee. Do not purchase the hard drive from the manufacturer unless they offer you a good price on it AND are preinstalling everything for you since they will typically be much more expensive. Look for your new 2.5" laptop hard drive from sources like Newegg or Tigerdirect (USA or Canada) online or check locally after you look up what it should cost you. I have seen many more Seagate drives fail prematurely than Western Digital drives (I am curious what yours turns out to have been).
You have to be a little bit crazy to keep you from going insane.