It voids your waranty and companies don't condone it.
It doesn't void the warranty. AMD don't lock the jumper on the FX series for you to get extreme speeds. On the AMD 64 range they let you decrease your jumper so you can get better memory bandwidth when overclocking (if you can't get the CPU very high.)
On my graphics card, it says in large font extreme overclocking, on the front.
There is software included with my motherboard for me to overclock in windows if I feel the need.
Overclocking is greeted hapily.
Compamies like DELL hate overclocking, so they make it impossible to do it. (with out hardware mods.)
If it doesn't boot, take out the battery leave it for about 15minutes to clear compltly (doubt there would be a jumper to do it quickly.) and don't go so far next time.