Motherboard 3 or 5 years (depending on model)
ASUS products have serial numbers that are 10 - 15 digits long. They have the following format:
1st digit: Year Manufactured (last digit of the year)
2nd digit: Month Manufactured (1-9, A-C)
3rd digit: Product code ("N" for notebook, "M" for motherboard, etc.)
Possible locations :
Parallel port
Side of PCI slot
Side of power connector
Underneath/backside of board
Side of CNR slot
Here a link how to read serial number to find the product date.
http://livesupport.asus.com/serialnumbers.html