If a GRUB boot menu appears on the console at some point when you boot the system, it is running some flavor of 4.x software. You can select the second boot option (Recovery) to re-image the sensor and reset the passwords.
If no GRUB prompt is displayed, you will need to re-image the sensor using the new 4.1(4) system image. But first, you need to verify the BIOS version currently installed on the sensor. The BIOS version will be displayed during the earliest part of the boot process. If it is not "5.1.7" (earlier 4215s shipped with version "5.1.3"), you will need to download and install the 5.1.7 BIOS upgrade from:
Follow the instructions in the associated readme file to load the new BIOS. Once you have upgraded the BIOS to 5.1.7, you can TFTP-boot the "IDS-4215-K9-sys-4.1-4-S91a.img" from:
As with the BIOS update, follow the instructions in the associated readme file to install the system image.
Once the system is re-imaged (it will reboot several times first), you can login using the default account/password (cisco/cisco) and run setup to configure the sensor.