BBB has no response after I changed IP and boot disk.

Hello everyone,
At first I’d like to change the IP address of my BBB thus connect multiple BBBs with my PC. According to https://groups.google.com/forum/#!topic/beagleboard/mn1VKZBV4sY ,I edited /etc/udhcpd.conf changing IP from 192.168.7.1 to 192.168.8.1, then changed usb0 ip to 192.168.8.2. There are not /usr/bin/g-ether-load.sh and /etc/udev/rules.d/udhcpd.rules in my BBB.

However, after reboot I can’t connect the BBB anymore using 192.168.7.2 or 192.168.8.2, but still have access to boot disk. Then I delete all files on this disk, copy all files from another BBB’s boot disk to this disk.(A big mistake!!!) After this I cannot access boot disk or connect it through USB.

Now only LED0 is blinking, indicating that the CPU is not working. What can I do now? Any suggestions are welcomed!

reflash with a new image

So how to effectively change the IP address to others? I tried and searched a lot but no one works.