XIAO BLE nRF52840 -- driver does not install under Windows 7

recently moved from XIAO to XIAO BLE using the Arduino IDE. Unfortunattely under Win7 it would not auto-install the required driver (yellow exclamation mark in device manager).
Works fine on a Win10 machine of room-mate. Any hints would be appreciated (short of installing Win10 which runs slow on the Laptop I am using).
Thanks in advance – Thomas