Solved Linux EFI partition shows in Windows as Z:

When I open up Explorer I see a "Local Disk (Z:)" drive that is 500MB in size with 6MB in use. If I try to open it, even as administrator, I am denied access. If I open Disk Management I don't see a Z: drive listed anywhere. This is a custom built computer, so there are no "recovery" partitions.

Using a Live Linux boot CD I was able to find a partition that matches the size and it looks like my EFI partition. If this is what Z: is, it should not have a letter or be visible at all, except in Disk Management.

How did Z: come to be? I did nothing to try and access the EFI partition. It just appeared on its own.

More importantly, how can I verify if this is actually my EFI partition? How can I get this partition hidden again without damaging the system?

@Calab

A 3rd party program like Minitool Partition Wizard (free), is almost a must these days.

I tried a trick to see the Z: drive under windows - Open Notepad as an administrator, then go to Open and select Z:. This is definitely an EFI partition but ONLY has an ubuntu directory in EFI. My actual boot EFI partition is on a different disk.

This kind of makes sense, since my PC is dual boot. But still... why is there a Z: drive? Disk manager doesn't show a Z: at all.

I was able to figure it out using Diskpart.

Use "list disk" to find the disk number of the disk that has the partition. Select the disk.
Use "list part" to find the partition that has the letter you want to remove. Select the partition.
Enter "remove letter=z" to remove the Z: from the selected partition.

Minitool Partition Wizard is a whole lot easier.

And it'll still work for the "next" issue that pops up.