You should be able to connect to two headphones (audio devices) at the same time. But for other devices, only one KIND of each device, such as a mouse + a keyboard + a speaker at the same time.
However, there are factors that can reduce the number of devices that will work simultaneously. Devices that require high data transfer speeds, such as an audio device, will limit the available bandwidth for other devices to use and can cause problems. Additionally, certain Bluetooth profiles can only be used by one device at a time, such as the Advanced Audio Distribution Profile (A2DP) which is used by most audio devices, so usually only one audio device will work.
Note: Please install BlueSoleil on your PC when you want to connect two headphones.