Delete the following files, then run the installer again:
C:\Users\Kids\AppData\Roaming\.minecraft\versions\1.17.1\1.17.1.jar
C:\Users\Kids\AppData\Roaming\.minecraft\libraries\net\minecraft\client\1.17.1-20210706.113038\client-1.17.1-20210706.113038-slim.jar
C:\Users\Kids\AppData\Roaming\.minecraft\libraries\net\minecraft\client\1.17.1-20210706.113038\client-1.17.1-20210706.113038-extra.jar
C:\Users\Kids\AppData\Roaming\.minecraft\libraries\de\oceanlabs\mcp\mcp_config\1.17.1-20210706.113038\mcp_config-1.17.1-20210706.113038-mappings-merged.txt