Esta solução é proposta pelo respeitado TenForums.com: link
Crie um arquivo em lotes com as seguintes informações:
@echo off
:: Created by: Shawn Brink
:: http://www.tenforums.com
:: Tutorial: http://www.tenforums.com/tutorials/23504-users-personal-folders-restore-default-location-windows-10-a.html
taskkill /f /im explorer.exe
timeout /t 2 /nobreak >nul
if not exist "%UserProfile%\Downloads" mkdir "%UserProfile%\Downloads"
reg add "HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders" /v "{374DE290-123F-4565-9164-39C4925E467B}" /t REG_SZ /d "C:\Users\%USERNAME%\Downloads" /f
reg add "HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders" /v "{374DE290-123F-4565-9164-39C4925E467B}" /t REG_EXPAND_SZ /d %%USERPROFILE%%"\Downloads" /f
reg add "HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders" /v "{7D83EE9B-2244-4E70-B1F5-5393042AF1E4}" /t REG_EXPAND_SZ /d %%USERPROFILE%%"\Downloads" /f
attrib +r -s -h "%USERPROFILE%\Downloads" /S /D
timeout /t 1 /nobreak >nul
start explorer.exe
E execute o arquivo bat. Em seguida, mova os arquivos do local antigo para o novo.