Because Windows 7 does not natively support Bluetooth 4.0 or CSR chipsets fully (unlike Windows 8, 8.1, and 10 which have generic inbox drivers), the MBT-503-03 requires a proprietary driver package to function correctly.
Note: Do not download drivers from untrusted sites. Prefer vendor support pages or well-known driver repositories. Bluetooth mbt-503-03 driver windows 7
Many of these older dongles use a Broadcom chipset. You can try the WIDCOMM Bluetooth Software Because Windows 7 does not natively support Bluetooth 4
Whether you have a 32-bit or 64-bit system, here is how to track down and install the correct driver for your dongle. Identifying the MBT-503-03 MBT-503-03 Bluetooth mbt-503-03 driver windows 7
If you want, provide the hardware IDs (VID/PID string) from Device Manager and I’ll find specific driver download links and exact installation steps.