Have you ever noticed the Windows.old folder in your system directory after re-installing Windows? The folder holds a copy of your previous installation. With its help, you can restore data or salvage personal files and program settings you forgot to back up.

Since Windows.old is a complete backup of your system and user data, it comes to at least 3GB, plus anything you installed or stored under your user profile on top of that. Should you be short on space, here's where you can get a big chunk of storage space back. I'll also discuss Windows Rollback for those of you running Windows 10 Technical Preview.

What Exactly is Windows.old?

When you upgrade or refresh Windows or when you re-install on top of an existing installation without formatting the drive, your old Windows files will be preserved in a folder called Windows.old. You'll find it in the root folder of your new Windows installation, typically C:\Windows.old

Windows Old Folder

Since it contains the files of an entire Windows installation, including user profiles and any personal files you might have stored within them, this folder often totals over 10GB, space you could probably use otherwise.

How to Retrieve Files from Windows.old?

You should hold on to the Windows.old folder until you're certain that your current setup works smoothly and you don't need any files from this backup. Should you notice you're missing something, though, you can dig into your Windows.old folder. It's even possible to restore the previous Windows installation, but that's complicated and potentially messy. It's best to start from scratch.

To restore data from the Windows.old folder, you can either access it and extract files manually or you can run the Recover personal files tool. When the option Apply repairs automatically is checked (default setting), personal files from the Windows.old folder, including any Users folders and Documents and Settings, will automatically be copied back to their original locations. Click the following link for a direct recovery tool download from Microsoft.

Recover Personal Files

How to Remove Windows.old?

You could simply wait for 28 days. The creation of Windows.old also triggers a scheduled task that will delete the system files contained within the folder after four weeks.

You have only 28 days to retrieve most files from the Windows.old folder, beginning from the time you install, upgrade to, refresh, or reset Windows. After that time, most of the content of Windows.old (...) is automatically deleted. Files and settings stored in the Users or Documents and Settings subfolders of Windows.old might still be available in Windows.old after 28 days, but other files, including Windows installation files, will be deleted.

Source: Microsoft

To remove the folder before its time is up, search for Administrative Tools, double-click on Disk Cleanup, select the system disk, and click OK. In the results window (left), click the button Clean up system files and confirm the selection of the system drive again.

The following scan could take a little longer. The new results (right) will contain the option Previous Windows installation(s). Check it and click OK to purge these files from your computer. You will be asked to confirm the selection; click Delete files to proceed.

Disk Cleanup

How to Remove the Windows 10 Rollback Boot Option?

If you're a Windows Insider dual or multi-booting the Windows 10 Technical Preview, you might have noticed that a Windows Rollback option added itself to the boot menu. Here's a word of warning: DO NOT select this option, unless you really want to revert to the previous build. The rollback process will launch immediately, without an additional confirmation and it is unstoppable. That said, if you do want to downgrade, it does work and it's fast; I "tried" it twice.

It's way too easy to accidentally select the wrong boot option. Once you find that the new build works fine, I strongly recommend you remove the rollback boot option. You can of course keep the Windows.old folder and thus maintain the option to roll back.

To edit the boot menu, click Windows key + R, enter msconfig and hit Enter. Switch to the Boot tab, select the boot option you'd like to remove, and click Delete. I already removed the rollback option, which is why it is not shown in the screenshot below.

Windows 10 Boot Menu

Has Windows.old Ever Saved Your Bacon?

Given how frustrating it can be to lose your personal files, Windows.old is a very smart feature. Even when Windows no longer boots, your files are still there. You can access them and make a backup with a rescue disk. Knowing that they will automatically be backed up, however, is reassuring. Just don't format the drive before you re-install.

We'd like to hear from you! Has this automatic backup ever helped you recover files you would otherwise have forgotten about and lost? How could Microsoft make Windows.old better?