Windows not seeing external drive

I've just moved flat and when I setup my desktop PC again, Win 10 does not see the external USB 3.0, 1 Tb disk drive I have on my system. I had previously noticed this with another small drive but hadn't got round to dealing with it.


My flash drives - 2.0 and 3.0 - all work fine, as do my internal drives ( 1 x SSD and 1 x disk drive), so the issue seems to just be with external drives.


The drive is present in Device Manager, and the driver is fully up to date. My system automatically updates Win 10 so that's up to date too.


What can I do to make this work?


Thanks.

My system is:
- Intel Core i7 3770K Processor 3.50 GHz (No Overclocking)
- Asus P8B75-M LX Basic Micro ATX Motherboard
- 16GB Corsair PC3-12800 1600MHz DDR3 Memory (2 x 8GB sticks)
- Samsung 840 series 250GB Solid State Drive
- 2000GB 7200RPM Hard Disk
- Windows 10 Home 64 bit

What does disk management say it may just need a drive letter assigned

You're right - the drive letters are wrong - though I'm baffled as to why these would change.

Disk management is not something I'm familiar with, but it showed the missing drive without a drive letter so I added one ('E' which is what it should be), but this sent the machine into some sort of crisis with desktop icons appearing and disappearing and everything slowed to a crawl. It didn't recognise it as an NTFS drive, but showed it as RAW (don't know what that is...). So I re-booted and removed the drive letter I'd added, and the machine is now behaving normally again but still doesn't recognise the drive.

I've attached a screen grab of the Disk Management screen. The 'missing' drive is indicated as 'disk 3 partition 1'

Because I have crucial data from the last two weeks that is not backed-up, re-formatting is not an option.