This KB article shows how to re-image a WWT-P-7400W step by step. 

Proceed with caution. Re-imaging the OS will wipe out all data on your OS disk. 

• Boot to bootable USB. 
  
  • Click here for instructions on how to create a bootable USB: https://support.hanwhasecurity.com/hc/en-us/articles/360052154954-Wave-How-to-create-a-bootable-USB-flash-drive-for-OS-re-image

• Select language.

• Select install now.

• Accept terms and continue to the next screen.

• Select “Custom” to clear out old configuration and install a fresh install.

• You will need to identify your OS drive. You must clear out all partitions to have the total volume (disk X) completely unallocated.

• Select “Drive options“ to delete all partition under appropriate disk.

• Once you have deleted all partitions select the disk to load the OS and click Next.

• Once the OS is installed the system will reboot and you will be on your login/main screen.