Mega2560 identify itsely as arduino uno

Hello,my friends.

Sorry if my english is not really good: i'm chinese.My mega2560 identified itself as an arduino uno.I want to know how to update the 8u2

fireware because i see someone solve the problem after update it. (the arduino IDE runnin on windows7 ,32bit)

if you have questions for me to help for my problem, you can ask me and it will be a pleasure for me to answer to it!

thank you.