HDD might be toast.
Like rgd1101 suggested, try using the HDD with another computer.
Easy way of doing this is getting an external HDD case for 2.5" HDDs and putting it in there and seeing if another computer can access the drive. If its still accessible, the drive is most likely okay, but would recommended testing the drive as well. Backup the data files if you can.
It might have affected the SATA controller when you took it out with the battery still in the laptop.
If that's the case, and you're out-of-warranty, buy a new laptop. You'd have to replace the motherboard, and it is not worth the cost. HP's cost for a motherboard replacement is $329.