Standard compression formats (like 7-Zip or WinRAR) typically achieve compression ratios between 30% and 60% for executable data and raw assets. It is mathematically impossible to losslessly compress a 15 GB game file into 100 MB. If a file claims such drastic reduction, it is either a misrepresentation, a "ripped" version (with music/videos removed), or a malicious trap.
Many sites offering "highly compressed" games use these files as "traps" to distribute trojans, spyware, or fake antivirus software. Broken Game Files: download the elder scrolls v skyrim highly compressed
Here is the truth: You do not need to risk a shady download. it is either a misrepresentation