You should see a file named HDDREG.EXE , HDDREG_CN.EXE , or sometimes HDDSRV.EXE (depending on the version).
Safely eject the drive, restart your PC, and boot from it again. 💡 Best Modern Alternatives to HDD Regenerator Hdd Regenerator Bad Command Or Filename
If the "Bad Command" error persists even after a re-flash, you might want to try a built-in tool like Windows Check Disk (chkdsk) from a recovery environment as a safer first step. ULINK DA Drive Analyzer You should see a file named HDDREG