The is a common Bluetooth adapter, often based on the Cambridge Silicon Radio (CSR) chipset. While it works plug-and-play on Windows 8.1 and 10, Windows 7 users frequently encounter driver issues due to missing native Bluetooth stacks.
If you are still having trouble, providing the from Device Manager (Properties > Details > Hardware IDs) can help identify the exact driver needed. Bluetooth mbt-503-03 driver windows 7
Since the MBT-503-03 is almost certainly a CSR device, the most stable driver comes from the chipset creator (Qualcomm/CSR). The is a common Bluetooth adapter, often based