If you specifically need the 6.03 legacy version, check MajorGeeks or OldVersion.com , which maintain archives of older software builds. Quick Tips for Using WinRAR Portable
The "Portable" version is especially handy because it doesn’t require a full installation. You can run it directly from a USB drive or a folder on your desktop, keeping your system registry clean. Download File 6.03 Portable.rar
Even if you prefer 6.03, newer versions like RAR 6.10 offer better support for non-Unicode file names and improved security. If you specifically need the 6
After downloading the .rar or .zip file containing the portable app, extract its contents to a folder before running the executable ( WinRAR.exe ). check MajorGeeks or OldVersion.com