: Ensure you are using a high-quality USB cable and try a USB 2.0 port instead of USB 3.0, as legacy flash drivers can be sensitive to newer port speeds.

: Select Update driver > Browse my computer for drivers > Let me pick from a list .

: You can also check Advanced options > Optional updates in Windows Update settings to see if Microsoft hosts a compatible version.

: Hold Shift while clicking Restart . Go to Troubleshoot > Advanced options > Startup Settings > Restart . Press 7 or F7 to "Disable driver signature enforcement".

: If Windows refuses the new driver, use the Add legacy hardware option in Device Manager to force the installation.

: Most users download the Flashtool drivers, which include "S1 Boot" and "S1 Service" drivers for various Xperia models like the Xperia Z or C.

: Connect your phone in Flash Mode (usually by holding Volume Down while plugging in the USB). Right-click the "S1 Service" or "Unknown Device".