@MiguelNuno
  • Ensure you have US/EU model 3590 with HWID 1258: [Only registered and activated users can see links. ]
  • Ensure your US/EU 3590 has latest firmware Version 8.50 (connect to GarminExpress and update if it has a lower version)
  • EXTRACT the Flash Kit ZIP file directly to a CLEAN microSD card (look behind Spoiler below)
  • Ensure your device is fully OFF, not just in standby mode
  • Insert the card
  • Power on (if the battery is low, connect to an external power source [NOT a computer USB port] which will power it on)
  • "Loader"/"Software Loading" or similar message should appear on screen during start-up
  • Wait for it to finish the flash and re-boot itself, then remove the card.

Spoiler: Flash Kit
[Only registered and activated users can see links. ]

"Apps" screen should now have Media Player and Video Player icons. Keep the files from the card in a safe place. In the card root you should now additionally have '41_BUP.bin' and '140_BUP.bin'which are copies of your device's non-vol and features regions. In the 1258 folder there will also be a new file named 'last_id.bin' which must be removed before re-using the files or it will prevent further flashings.

Disclaimer: All care taken in preparation but no responsibility accepted if your device is damaged. Follow the above instructions EXACTLY.