: Open the USB drive, navigate to BootCamp > Drivers , and open the specific hardware folder (e.g., Broadcom or Intel). Run the individual driver installers manually. To help give you the right advice, please let me know: What Mac model and year are you using? Which version of Windows are you trying to run?
The officially supported Mac models for version 5.1.5621 include: Supported Mac Models boot camp support software 515621