Just wondering if you ever got this to work? I have a similar system (PB410 Legend 125) with the same issues. Removed leaking battery, cleaned the area, and hooked up an external battery. See this post for details on that.

I would also get the shutdown failure message and could press F1 to continue or F2 to enter setup utility. Pressing F1 would flash the light on the A drive and then repeat the same message. Pressing F2 would just lock up the system. This was all with the external battery (3 x AA) connected to the 4 pin external battery connector. Having no luck with that, Iím assuming there is an issue with the BIOS chip. Itís an EEPROM, so not sure if it somehow got corrupted.