Many driver download sites bundle malware/adware. Never run random .exe files named "Gaintech_USB_Switch_Driver.exe" unless you are certain of the source.
Gaintech has multiple variants (e.g., GUH2S4, GUH2S2). Look for a sticker on the device. The driver depends on the internal chipset, not the "Gaintech" brand. gaintech usb 2.0 auto sharing switch driver
The "auto sharing" feature is hardware-based (sensing voltage/current changes on the data lines). If it doesn't work, the switch may be faulty or incompatible with your USB device (e.g., some external drives or scanners with proprietary polling). Many driver download sites bundle malware/adware