Connect the Speakers to the PC. Go to the Device Manager/Hardware and Sound and Finally the Sound Panel. The Bose Speakers should be shown in the Playback panel and if there is an icon for them, make them the default playback device.
If that does not fix it, the windows status may be corrupted. To fix that there are two possibillites.
1. If the speakers are detected correctly in the Device Manager, RIGHT click on the entry for the Speakers and then LEFT click "Uninstall". Then restart the PC and when Windows starts it should detect and reinstall them.
2. If the speakers are not recognized by Windows, with the Speakers connected there should be an unknown device listed in the Device Manager, USB listing. Uninstall the unknown device in the Device Manager. Disconnect the speakers and then restart the PC. After Windows starts, connect the speakers and they should be detected and reinstalled.