If your goal is to save space, it is better to download the full game and then use a tool like CompactGUI (which uses Windows 10/11 built-in compression) rather than downloading a potentially corrupted "highly compressed" archive from an untrusted source.
Many sites offering "highly compressed" links bundle the downloader with adware or malware. Always ensure your antivirus is active and use reputable community-verified sources. Where to Safely Find the Game elder scrolls oblivion highly compressed download link
Install the game to a folder like C:\Games\Oblivion to avoid Windows permission issues that block mods. If your goal is to save space, it