How can I reinstall the MikroTik RouterOS™ software without losing my software license?
You have to use CD, Floppies or Netinstall procedure and install the MikroTik RouterOS™ on the HDD with the previous MikroTik RouterOS™ installation still intact. The license is kept with the HDD. Do not use format or partitioning utilities, they will delete your key! Use the same (initial) BIOS settings for your HDD!