We need more info here:
1. What is the capacity and model number of the hard drive?
2. Is the old drive still working?
3. Or are you replacing a faulty drive?
4. If you're replacing a faulty drive, when you reinsert the faulty drive, does it at least pick up the drive in the Bios?
If the old drive also isn't picked up, it may be a faulty connection on the motherboard, or you may have a faulty hard drive controller.
However, If the old drive is detected in the BIOS, there may be a compatibility issue with your new hard drive and your laptop.