Hold the "Setup" button for 10 seconds. If a secret menu doesn't appear, you may need VCDS to enable it. Note your "Delivery Part Number" and "HW-Version."

: The system will reboot multiple times. Do not touch anything until a "Success" message appears and the disc is ejected .

The phrase "rns 510 firmware 5238 download free free" is searched over 1,000 times per month – proof that the legendary RNS 510 refuses to die. But a free download is worthless if it destroys your unit. Take 10 minutes to verify your hardware revision before you take 30 minutes to flash. Do that, and your RNS 510 will serve you reliably for another five years.

Here's a more detailed installation guide: