Unable to access files

Hello @Douglas Pounder

Don't panic yet; what you're describing is common when you remove a Windows system drive from one PC and attach it to another.

First, enabling sharing on the Outlook folder won't help here. Sharing permissions apply when accessing files across a network. Since the old drive is connected directly through a USB adapter, you're dealing with the drive's NTFS permissions/ownership, or possibly encryption.

Before changing permissions, please check whether the old drive is BitLocker/device encrypted.

Open Command Prompt as Administrator and run:

manage-bde -status

Find the USB-connected drive in the results. If it shows BitLocker protection and the drive is locked, don't change permissions, format the drive, or initialize it. You'll need the BitLocker recovery key to unlock it. Microsoft provides guidance for locating a recovery key here:

If the drive is not encrypted and Windows simply says you don't have permission, this is probably because the files are still owned by the user account/SID from your old Windows 10 installation.

In that case, rather than changing permissions on the entire old Windows drive immediately, start with the folder containing the files you need:

Right-click the folder > Properties > Security > Advanced

Check the Owner shown at the top. If it references an account from the old computer or an unknown SID, select Change, choose your current Windows account, and, if appropriate, apply ownership to the files and subfolders.

Windows also provides the takeown and icacls commands for administrators, but don't use recursive commands against the entire old Windows installation until we've confirmed that this is just an NTFS ownership issue. It's better to recover your personal data first without unnecessarily altering the original disk.

Another possibility to check: if individual filenames appear green in File Explorer, or if Properties > Advanced > Encrypt contents to secure data is selected, those files may have been encrypted using EFS (Encrypting File System). Taking ownership won't decrypt EFS-encrypted files; you would need the encryption certificate/private key from the original Windows installation.

For your Outlook data, also tell us exactly what you're trying to recover, particularly whether you're looking for a .pst file. If the mailbox was using Exchange/Microsoft 365 or Outlook.com, much of the mailbox may already be stored on the mail server and can be synchronized again without recovering the local Outlook data file.

To prevent this on the replacement laptop, you generally shouldn't weaken Windows file permissions just to make a future disk removal easier. Instead, back up important files to another drive or OneDrive and, if BitLocker/device encryption is enabled, back up the recovery key somewhere you can access it independently of that computer.

Could you post the exact access-denied message and the output of manage-bde -status for the old drive? Please remove any personal information before posting it. That will tell us whether we're dealing with BitLocker, NTFS ownership, or something else before making changes to the disk.

References:

Find your BitLocker recovery key

Microsoft Learn - takeown

Microsoft Learn - icacls

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All OneDrive files reside at onedrive.com. When you get your new computer, you'll just need to sign in to OneDrive. I wouldn't link OneDrive to that old OneDrive folder; keep it only as a backup.

Please see the suggestions in this thread to help you take ownership and gain access to the old folder.