and with nothing to lose, you should be able to set the boot device to the CD and have XP completely repartition, format and install. I'm guessing your boot order was C: D: so, when you first inserted the NT disk, your BIOS saw nothing on C: and went to the CD ROM drive. The partial installation created a bootable partition on C: and your BIOS is set to try that one first. Set the boot order so the CD ROM is first and you should be able to start over.
I recently had to replace my failed hard drive in my lap top. I grabbed what I thought was the operating system disk for the laptop--Windows XP--and got as far as the prompt asking for the product code before discovering it was the OS disk from my last computer, which ran on Windows NT. I removed the NT disk and inserted and tried to run the XP OS disk, but the NT system keeps booting up at the product code entry screen (which I can't enter b/c I no longer have that computer). So--how do I override the NT OS to replace it with XP. Help?