When accepting a picture via Bluetooth I accidentally enabled the checkbox Always do this for Image files from ...
Now pictures are always accepted from this device and I am unable to change the folder to save them in.
How can I reset this setting so the dialog appears again?
First of all, even though in Windows 7 the Bluetooth settings dialog always looks the same, there are at least two different Bluetooth stacks available which differ significantly in capabilities.
One of them (Microsoft/Widcomm/Broadcom?) can easily be recognized because it has the Bluetooth Device Control window that opens when you double click a Bluetooth device in Devices and Printers. This one is also the one that has the dialog mentioned in the question.
The other one (Toshiba?) features a "Receive file" entry in it's Bluetooth tray icon menu and does not have these Bluetooth Device Control windows. The question (and answer) does not apply to this kind of Bluetooth stack.
If you feel uncomfortable editing the registry there is a UI method to re-enable that dialog, however it's a bit cumbersome.
Bluetooth Device Control windowAuthorization Options section and expand itAlways allow this device to connect for all operations and ApplyRequire confirmation for all operations to and from this Bluetooth device and ApplyThe next time you send a picture from this device, the file receive dialog will appear and give you the chance to choose the destination folder for the received file again.
If you do feel comfortable editing the registry, it's much easier:
HKLM\SOFTWARE\Widcomm\BTConfig\Devices (not HKCU, there is a very similar subtree there which I found to have no effect whatsoever)Name valueImageFileOption (or AudioFileOptionetc.) value to 0 (or just delete the whole device key to reset all setting to default)