Re-download part3.rar . Multi-part archives are very sensitive to download interruptions. Ensure you are using the latest version of or 7-Zip . Security Warning
If you receive a "Checksum Error" or "Archive Corrupt" message during extraction: RIDE.3.CODEX.part3.rar
After installation, look for a folder named inside the mounted ISO. Copy all files from the CODEX folder. Re-download part3