Is the hard drive still good?

You can have a laptop motherboard short out without it affecting the hard drive. I f you purchase the exact laptop with exact model # and specs you should have no problem swapping hard drives. I recommend storing the hard drive from the new laptop in a safe cool and dry place in case your new system crashes, you have a spare to keep you going. A good practice is backing up your files whenever their are changes in your file library. You never know what unfortunate little accidents lies ahead.