Error 0x800701b1 on Windows usually appears when there's a problem accessing a drive, often an external hard drive or USB. To fix it, try plugging the device into a different USB port, especially a USB 3.0 if available. You can also update or reinstall the drive's drivers via Device Manager. If that doesn't work, check the drive for errors using the Windows Error Checking tool or run chkdsk in Command Prompt. Make sure your system has enough power if using a portable drive—use a powered USB hub if needed.