1. right click my computer and then click manage
2. Click on disk management, should be on the left towards the bottom of the list.
3. look for your drive and right click and delete the 2.0 tb partition.
4. now right click on the white "Disk #" box and hit convert to GPT
5. Now right click on the Unallocated space (It has a black bar above it) and click new simple volume.
There you go, you should now have your full 3 tb hard drive ready to be used!
Please note that I used windows 7 ultimate 64 bit and this is what worked for me.