I looked on HP's website and couldn't find any information about BIOS recovery. A retail Asus motherboard usually has a BIOS recovery routine, although a floppy drive might be needed.
You can call or e-mail HP tech support and see if they have any suggestions.
I can't think of any other options besides replacing BIOS chip or motherboard.
One should only flash a BIOS when absolutely necesary unless there is a recovery option available. It's a procedure that's done much too often by end users and can result in a useless PC -- as you found out.