Disable "Real-time protection" in Windows Security before starting the installation.
Before diving into fixes, it helps to know the culprit. This isn't usually a "broken" download, but rather a system environment issue:
FreeArc is an older compression format and sometimes struggles with non-Latin characters or long paths. C:\Games\Skyrim
If it finds missing data (e.g., 99.8% complete), it will redownload the tiny corrupted portion. 5. Rename Folders (Avoid Special Characters)
If you are using a laptop, ensure it is plugged into power and set to "High Performance" mode. Decompressing FreeArc archives puts a massive load on the CPU, and power-saving throttles can cause the archive to "time out" and report as corrupt.