What the Local Disk Z:

[Taz1]

Out of the blue I have a Local Disk Z: on my PC that wasn't there before.  When I click on it it says you don't have authorization to access drive? Can someone explain?

[PeerOne]

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@Taz1 wrote:

Out of the blue I have a Local Disk Z: on my PC that wasn't there before.  When I click on it it says you don't have authorization to access drive? Can someone explain?

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What other computer are on your  workgroup or network? Do you have something plugged into the USB?

[Shempstir]

I got this same Local Disk (Z:) showing up out of no where.  When I click on it I get the following:

I close the window. When I scan the drive What I find is Z:\EFI\Microsoft\ and Z:\EFI\HP\ folders with I think are boot\system files. one of the file I was able to catch was: Z:\EFI\HP\SystemDiags\SystemDiags.s12.

I notice that drive Z:  Around the time I was trying to install a new HP Envy 5540 printer. 

With this more information can you tell me and the others what this is? 

I do not what to hit Continue until I know what it is!!

It not a very big Disk either

Could it be deleted?

[Astronomer27]

I solved this problem today, working with HP support.  It may be related to printer software issues.  I see that your problem started when you attempted to load HP printer drivers.  My HP LaserJet Pro300 is wirelessly connected to my HP Windows 8.1 desktop computer. 

In my case, I believe that the problem arose when I responded to error messages that HP Support Assistant incorrectly posted.   When I did, the local Z:\ drive simply appeared--I never did anything specifically to create it. 

Here are the steps that resulted in eliminating my local Z:\ drive :

1. Disconnect the power cord on the printer.  Leave it unplugged.
2. Shut down your PC.
3. Power on your PC.  Log in via your normal procedures.
4. Check the icon "My Computer", "This PC", or equivalent path to the root directory of the PC.
5. When I did, the Z:\ drive was gone.  But I still had a few verification steps to follow thereafter. 
6. Plug in the printer, wait until it fully initiates.  Leave it powered on and initiated, as you normally would when starting your machine. 
7. Shut down your PC.
8. Power on your PC.  Log in via your normal procedures.  Verify that the PC can see your printer. 
9. Check the PC's root directory as in Step 4 above.  Hopefully, the Z:\ drive will  remain gone.
10. Restart your PC, leaving the printer powered on an initiated as in Step 8 above. 
11. Again (hopefully) the Z:\ drive will  remain gone as in Steps 4/5 and Step 9 above.  This did work for me. 

By the way, in Windows 8.1, "Shutdown/Power On" is a different process from "Restart".  That's the reason for Steps 7-8 AND Step 10.  Hope this helps.

[DNAstrom]

I have the same problem when responding through hp support assistant and disable guest account ,since then I am seeing this local drive Z , there is some problem in new version of  hp support assistant 8.xx    They should fix it ASAP !!!

[wmhgreen48]

Same problem here...and it wiped out a network mapping I had for Drive Z!  Chaos ensued...FIX THIS!

[guerrez]

I had suddently as well on my HP Pavilion with Win 10 Home Edition. I was not installing any program or driver. Please advice!

[iSaneLunatic]

Well. I have a lot of technical experience but why in the world windows has to create a partition I have no idea. I experienced the same issues that you all did. Drive Z appears for no apparent reason, denied access. No security tab to take ownership and gain access. Sooooo, I took control of my own problem...

I enable the raw administrator. Then opened a command prompt as administrator (probably could have did this without enabling the raw admin, but why take chances. Yes I'm the same guy that brings a tank to a knife fight.) I found the following on the root of the drive.

Z:\>dir
 Volume in drive Z has no label.
 Volume Serial Number is 7A95-624B

 Directory of Z:\

09/05/2016  07:10 PM    <DIR>          EFI
               0 File(s)              0 bytes
               1 Dir(s)     170,754,048 bytes free

in that folder I found:

Z:\EFI>dir
 Volume in drive Z has no label.
 Volume Serial Number is 7A95-624B

 Directory of Z:\EFI

06/27/2016  10:52 PM    <DIR>          .
06/27/2016  10:52 PM    <DIR>          ..
06/27/2016  10:52 PM    <DIR>          Microsoft
06/27/2016  10:52 PM    <DIR>          Boot
09/05/2016  07:10 PM    <DIR>          HP
               0 File(s)              0 bytes
               5 Dir(s)     170,754,048 bytes free

Z:\EFI>

Question, why in the %$@! is this partition a boot partition???

Next I ran disk management and got

two part ions that do not have a drive letter or a name. One of them matches the size of this drive Z so that the one were after. It says its a EFI system part ion, this would make sense (remember the root has a directory called EFI).

What is a EFI partition? Lets ask Google (Google knows everything).

Per Wiki:

Jump to: navigation, search

The EFI system partition (ESP) is a partition on a data storage device (usually a hard disk drive or solid-state drive) that is used by computers adhering to the Unified Extensible Firmware Interface (UEFI). When a computer is powered up and booted, UEFI firmware loads files stored on the ESP to start installed operating systems and various utilities. An ESP needs to be formatted with a file system whose specification is based on the FAT file system and maintained as part of the UEFI specification; therefore, the file system specification is independent from the original FAT specification.[1][2]

ESP contains the boot loaders or kernel images for all installed operating systems (which are contained in other partitions on the same or any other local storage device), device driver files for hardware devices present in a computer and used by the firmware at boot time, system utility programs that are intended to be run before an operating system is booted, and data files such as error logs.[

in a nut shell this partition should NEVER have appeared on your device/pc. Oh it should exist on it, but it is supposed to be hidden. So the question becomes why is it appearing? I smell a bug. 

Microsoft.. am I right?

By the way. A reboot made my drive go back into hiding.  I was happy, I told it "STAY THERE OR NO MORE TREATS FOR YOU!!!"

[dbm5blue5]

I have the same issue, but I haven't installed a printer. 

[iSaneLunatic]

It's not a printer issue. It's a Microsoft hidden partition for booting the computer.  For some reason it becomes visible at times as drive z.  I rebooted and that made it hide again.  View my post above for details.