Dropping a hard drive, especially while it is in operation (unless it is an SSD) will almost always kill the drive unless it comes with the fall detection ability present in some laptop hard drives. Tough luck.
As for the Windows CD, not entirely correct guys. You CAN get the ISO off of the internet, as long as you own a license key (and most laptops purchased already do on the bottom) so just buy a new hard drive, get the ISO from your source of choosing, and install the OS accordingly. We can't tell you where to go to get the ISO, but it shouldn't be too hard to figure out.