Need to uninstall windows from one hard disk

[Bopper]

I have windows installed on the c drive and on the d drive. I tried reformatting the d drive but now when I start the computer it still thinks I have two windows installed and asks which one I want to start. How do I erase the other one completely?

 

[JesterX]

Right Click on 'My Computer' > Properties
Click on the 'Advanced' Tab

Under Startup and Recovery > Clicking Settings
Click the 'Edit' button next to 'To edit the startup options ....'
The 'multi(0)disk(0)rdisk(0)partition(1)\WINDOWS' is the first partition and in most cases would be C. So you need to remove the other one under "[operating systems]"