|The Acer TravelMate 5520 does not have a BIOS password when it leaves the factory.|
If it has one now, it must have been set either by you or by a previous owner. We cannot help you with that.
The CMOS battery is inside the laptop. The laptop casing has to opened to access the battery - it could be a coin-shaped battery like those used in watches and calculators, or on some laptops it's soldered on to the mainboard and can't be removed.
See this: http://www.insidemylaptop.com/take-...