I was working on a Asus laptop... in Bios I set it up to boot from a USB (so I could install a new OS) and then the system would never boot again and never got to the point where I could enter Bios. Did everything the factory said to reset the Bios and even removed the Cmos battery but it never did boot again. Now I am wondering what really happend.
History of the Laptop. it had Windows 7 and the video kept locking up and system over heated many times. Asus said the laptop was bad. I put Ubuntu into the laptop to see how it functioned. and it never overheated and video worked fine. So then we decided to put Win 7 back in it and instead of the DVD I wanted to use a USB stick...
USB stick method could be finicky to install with sometimes. If your mobo boots (BIOS, device checks, etc), you didn't kill the mobo. You just need to reinstall OS properly. If your mobo doesn't boot at all (no video), you could have fried it during cmos battery removal time.
Unfortunately, for laptop mobo that doesn't boot, you really can't do much about it. You can try to reseat memory (usually 1 on the bottom that is user accessible, and 1 on top that isn't, so you have to remove the housing), and replace the cmos battery (works sometimes). but beside that, you would need to RMA it which means $$$$ if no under warranty.
I did try to replace the cmos battery and that did not change things and it is not worth spending money on. All data had been saved before I attempted to change the OS the 1st time. Oh well, I guess they die from time to time.