Accidentally reformatted a hard drive containing important documents and files? Fear not, says our Helproom Expert, all is not lost.
QUESTION After I discovered my PC had an unlicensed copy of XP, I installed a new, legitimate, copy and accidentally clicked Yes to format the C drive. I lost access to the contents of my external backup drive, and am now unable to open any of the documents on my D drive or my external drive. Windows claims I do not have administrator privileges, even though I am the sole user. I suspect this is because XP was reactivated on my C drive and the new copy of the OS has a different serial number. Ronald Edberg

HELPROOM ANSWER We don't have much detail about the external drive to which you've lost access, but we presume that you have some sort of backup system in place that copies your data from drive C to drive D.

The issue with changing drive letters is a frustrating one. Booting from a CD to install an operating system can often result in your drives and partitions being assigned different letters to the ones they have inside Windows. It's therefore of the utmost importance to take great care when selecting a partition for formatting. Looking at the drive letter alone may not be enough; also look at the reported size of the volume and whether it has any existing volume name associated with it. It's also a good idea to unplug any external drives before you begin, as they can simply confuse matters.

If you accidentally format the wrong drive, immediately stop the installation and attempt file recovery using a file recover software tool such as PC Tools File Recover, Paragon Backup & Recovery 11, or similar. Formatting doesn't destroy your data – it simply tells the OS to treat all usable space as available. It's not until you place new files on the drive that your original documents will be overwritten. Once new data is written to the drive, however, your original files will become irretrievable. If you're not familiar with the data-recovery process, the best option is to hand over your drive to someone who is.

Files created under a previous installation of Windows may have permissions configured that, by default, are not accessible to other operating systems installed on the same PC. To get around this you need to take ownership of the files. This must be executed from an Administrator account.

To take ownership of a folder you will first have to turn off simple file sharing if you have it enabled. Open Windows Explorer and choose Tools, Folder options. Click on the View tab and look in the Advanced Settings section for the ‘Use simple file sharing (Recommended)' entry.

Deselect this option and click Ok.

Next, right-click the folder over which you want to take ownership. Select Properties, then click the Advanced button on the Security tab. Select the Owner tab in the new window that appears and choose your account name (or Administrator) under 'Change owner to'. Also select the 'Replace owner on subcontainers and objects' entry, then click Ok. Click 'Yes' if Windows asks any further questions about taking full control.

You should now be able to access your files and folders. Note, however, that this won't be possible if you encrypted your files in the previous installation of Windows.

For full details and information on how to perform similar procedures in different versions of Windows, read Microsoft's support article.

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