A faulty power adapter can cause problems with laptops.
I can not tell you if your motherboard is fried or not without doing actual tests on it.
Laptops suffer from CPU heat sinks that get clogged with dust and various internal connection issues on pressure lock connecters also called Zero Insertion Force (ZIF) type connecters.
The major issue is corrosin on these contacts, nothing special has to happen for this to happen, it just happens.
If you intend to save this laptop on your own, I can offer you a link to a web site that may help you diagnose your problem.http://www.insidemylaptop.com/disassemble-...-f700-notebook/
Here is support from HP for your laptop http://h20000.www2.hp.com/bizsupport/TechS...p;submit=Go%20»
Manual and a lot of other information on your laptop. http://h20000.www2.hp.com/bizsupport/TechS...SeriesId=449877http://h20584.www2.hp.com/hpgt/guides/sele...SeriesId=449877
You can use all the links provided on the pages I have provided to hopefully find a solution to repair this laptop.
If anything it will be a learning experience on how to repair a laptop.