He saved the command syntax into a Notepad file on his desktop, titling it

Beyond simple typos, the error often points toward a lack of authority. Windows protects its core files through layers of security, requiring "Administrative Privileges" for any tool that modifies the system image. When a user attempts to run DISM from a standard prompt, the system rejects the command with Error 87, effectively telling the user they do not have the keys to the engine room. Resolving this is a matter of protocol: one must simply right-click the command prompt and choose to run it with the full weight of administrative power.

Let the process finish. This forces DISM to repair your PC locally using the 100% clean files from the ISO. Conclusion

Finally, you can verify the health of your system image. After the SFC scan is complete, you can run DISM /Online /Cleanup-Image /CheckHealth again to get an official status report. A successful repair will typically show a message indicating the component store corruption was successfully repaired, or that the image is healthy.

DISM /Online /Cleanup-Image /RestoreHealth /Source:D:\sources\install.wim /LimitAccess

If you’ve ever tried to repair a Windows system image using the Deployment Imaging and Service Management (DISM) tool, you might have been greeted by a frustrating message:

"Targeting," he whispered. "I need to target the install.wim file directly."

Having a USB with the correct install.wim file (matching your Windows version) means you can always use the /Source parameter without guesswork.

If you're running this from or from a recovery/blue screen ?