Recovering Buffalo WZR-HP-AG300H from bad firmware upgrade

Recently I managed to flash bad custom build of OpenWrt to my Buffalo WZR-HP-AG300H rendering it unbootable. See below for tips how to flash latest OpenWrt over TFTP from Windows XP client.

1. Download TFTP version of OpenWrt from 
http://downloads.openwrt.org/snapshots/trunk/ar71xx/openwrt-ar71xx-generic-wzr-hp-ag300h-squashfs-tftp.bin

2. Disconnect WAN cable from Buffalo

3. Connect PC to LAN port closest to WAN

4. Set PC IP to 192.168.11.2, netmask 255.255.255.0. No GW, no DNS. 
   Make sure any other network interfaces such as WLAN are disabled.

5. Create batch file named FOO.CMD with following content

:FOO
ARP -S 192.168.11.1 02-AA-BB-CC-DD-20
PING -N 2 127.0.0.1
GOTO FOO

6. Launch FOO.CMD

7. Type "TFTP -i 192.168.11.1 put openwrt-ar71xx-generic-wzr-hp-ag300h-squashfs-tftp.bin"
   in command prompt but DON'T press enter just yet.

8. Connect power cable to AP

9. As soon as network link goes up hit enter on TFTP command window. 
   It should return nearly instantly and red DIAG led starts to flash on AP.

10. Set PC network settings back to DHCP and telnet to AP. It should be now up with 192.168.1.1 IP.