It is possible to do, it involves changing the firmware on the drive itself. There are a few utilities and guides that are available but it's a tad risky if you don't know what you are doing. Available firmware also depends on the make of drive you have.
Strange suggestion but try searching on ebay for dvd drives as I came across people selling ones for laptops that listed they could supply it region free but at the buyers risk. They listed the utility used and linked to it.
If your not sure about doing it maybe it's time to open up the wallet!! Could be cheaper than getting a new drive if the unlock messes up.