Hmmm, if you use Restorator or something like this, you can't replace a file (explorer.exe for you), while it's in use.
You may look if there's another file next to yours, named "explorer.exe.backup" or "explorer2.exe".
If you find it, cut and paste your original explorer.exe to another folder, then rename your second file like the original one. Reboot and then it will be ok i think.
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