Só abri o bloco de notas e coloca isso

RAR registration data
SiM
Local Site License
UID=ca5575bd41c33ec5a2de
6412212250a2de7c818d537f99bcf0218861216f4ce0738e2ef7ad
8bc2514534357f5541ed60694c88f20734f7fa6ad968865654a57b
0f0edf295d607ce6fa6d6b3667401b413bdcbccca3152c8ab6abc5
931818a35674a26f065261f8bce32dfbce601d1aa079a3c54f79c7
adeacb886214457e000e50d6ff5329a2f516ebba72708a35f704db
3d30b1633de64c1bdc0c5c2b54710967dde4c9aab721b69460185e
a12e2906a44bc32601e8ef0028d453a1d8b40dd23b562696892555


e salva com este nome rarreg.key

e coloque na pasta do WinRAR (C:\Program Files\WinRAR)

No meu caso, C:\WINRAR