It is not safe to use free or public USB drives and other external devices. Here are a few things to consider when using external drives and devices:

1. Ensure the device is from a trusted source.
2. Perform a virus scan on the device before use.
3. Do not store sensitive information such as passwords or important financial data on the device.
4. Set up strong password-protection on the device.
5. Regularly back up your system.