Does the drive still spin? You should be able to hear it. If you can hear a regular click noise, rather than a spinning noise you have big problems.
Was it the main drive in a PC that will no longer boot properly? If yes, you can download a "live" copy of Linux, eg Ubuntu and run that that from the RAM to read the hard drive.
Alternatively, you will need to place the drive in a second desktop PC or purchase an external caddy and connect that to a second PC. Be warned- things get really messy if the drive was encrypted. If it was, you are unlikely to get any data from it unless you have a friend that work for the NSA.
Best case scenario, the boot sector is effed up, that can be fixed by using the Windows recovery console.
Either way, if you are not confident about using the recovery console correctly, you can find free software that will enable you to clone the drive first.