USB and/or 2tb+ HDD not recognized in windows (or offline)

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USB and/or 2tb+ HDD not recognized in windows (or offline)

Postby Sethioz » Thu Oct 15, 2015 6:04 pm

Well this problem is hard to describe, but it's quite common and can make you go nutz, so let me first describe the scenario and then explain the cause and provide a fix.

Here are the error messages and scenarios you might have:

1. HDD needs formatting, but you're not able to use full disk. For example I have 3tb drive and it only allowed me to format 380gb. In windows disk management it had 3 partitions, even tho i only had one on it and it did not allow to assign unallocated space.

2. The disk is offline because it has a signature collision with another disk that is online (in disk management)

3. You have external USB HDD, you took it out of the case and using it as internal, however HDD is not recognized or windows can't access it and says it needs formatting.
This was my case

If you have external USB HDD and using it as internal, then problem is that USB adapter reports the HDD as GPT partition, but drive is actually MBR .. or not exactly sure wtf, but that's my theory, because MBR (master boot record) does not allow more than 2tb partitions and you can have total of 4 partitions. GPT (GUID partition table) partition doesn't have those limits. So my guess is that USB adapter reports the disk as GPT, but it's MBR. So if you take the USB disk out of the case and connect direct, windows gets confused.

Fix: You need to convert MBR to GPT. This can be done by using windows "disk management". However you will lose all data on the drive if you do it by using windows disk management. There are other tools out there that can do this, i had a backup of the drive so i could not bother looking for other tools, i just converted to GPT and did a quick format. In disk management, right click on the drive (not partition) and you see option "convert to gpt", hit that and you're done. Then allocated the space by right clicking on unallocated space and create new simple partition.

If you don't want to lose data, google for partition tools. Partition Magic should be able to do it, not 100% sure.

anyway it's bit confusing, but i've heard this issue a lot and now i had it myself, so hope it helps. feel free to leave a reply if you need any help.
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