Xbox 360 HDD not detected

First let's double check that the external HDD works. Try to connect to a PC. If the PC detects the HDD, format the HDD.

The plug to your console to see it detects the HDD apply the Xbox Format again.

Hope that works!

Regards!

I am having a similar problem. I have an older Xbox 360 MW2 Limited Edition with 250 GB HDD. I recently purchased Xbox 360 Slim with 320GB HDD. I didn't want to use a flash drive as copying 200+ GB's of data may take a while. I purchased an Official
New Xbox Transfer Cable (Black cable that supports all Xbox 360 drives, so I thought). After connecting my old HDD to the cable and plugging it into my new Slim (all USB ports), it does not detect hard drive. I dont know if its cable or the transfer software
built into Slim does not support all Official Xbox 360 hdd's or what. I did remove my 320 Slim HDD and connect it to the serial ata portion of cable and it was detected. Maybe its the other port of the cable thats bad. Help....

[quote user="dt2live"]i formatted it to another type of format and now im trying to use it on my xbox 360 again. but it wont detect it.[/quote]Formatting an XBOX HDD via anything other than the console's HDD connector (A PC, a third party transfer cable)
destroys the custom partitioning and security data applied to the drive at the factory. The drive can never be used again as a 360 HDD.

The issue should be, that the Xbox 360 had a USB 2.0 HDD. For the Xbox One you Need a USB 3.0 HDD with at least 128GB. What are the specs of your HDD from your 360?

You could also check this links:

https://support.xbox.com/en-US/games/troubleshooting/console-doesnt-detect-external-storage

https://support.xbox.com/en-US/xbox-one/console/manage-storage

[quote user="ShownMoth28231"]

Just trying to get the HDD to boot up so I can swap the info to the new xbox

[/quote]This might be considered System Tampering (depends). What exactly do you mean by "swap" and "new" Xbox?

If you're trying to Transfer via an External Method of an older style HDD to a new one (with the Xbox 360 S), that is System Tampering and the Console will not detect the "old" HDD.