Well it's working at last
The story:
Opening the device manager didn't show a yellow ! sign, with the BEO5 connected. Disconnection and connecting again....no result.
There wasn't any "unknown device", strange....
Then I tried a different USB port (one that wasn't used for the BEO5). And there it was in the device manager, the yellow sign. Now I could install the driver.
So in order: Open the device manager, connect the BEO5 to an USB port (one that hasn't been used for the BEO5) and install the driver for the "device with the yellow ! sign".
Thanks keith for the help. Opening the device manager was the solution.