I have a 250gb internal Ultra ATA hard drive enclosed in a 2.0 Usb external case. I installed it and did the formatting and was displayed that the formatting was not complete. I have not been able to re-format the disk or do anything else. My computer does not recognize the drive but I can locate the drive on the control panel where I can "safely remove items." I am running windows xp2 on HP computer originally 40gb SATA. The package instructions said to leave the external drive on master so I left it at that.
During formatting and initializing I was able to name my new drive as k:.
I have read several other threads with my same problem but none of them mention how to fix it when it is not recognized in disk management.

The above seperates you from other posts about drive letter problems. Also, you say it is not recognized in Disk Management, which means it is totally NOT working. This doesn't look like a software issue. You may have a faulty enclosure.

Have you tried to format it in Safe Mode... Just curious?

No, I cannot access it in any way.