There are two possible solutions.

Instructions:

1. Browse to your system folder (probably c:\windows)
2. A warning message appears
3. Click "Show folder content"
4. Click "Tools" in the menu bar
5. Click "Folder options..."
6. Click "View" tab
7. Click"Apply to all folders"
8. Press ok!
9. Restart windows explorer and warning message will never be seen again when browsing system folder

or

1. Start windows explorer (Windows key + E)
2. Go to "Tools" in the menu
3. Click "Folder options...)
4. Click "View" tab
5. Scroll down and disable "Hide protected operating system files (recommended)"
6. Click ok!

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