If you have a Wii and you bought it here in China, it's probably modded. If you are playing the 5RMB games you buy at the local electronics markets, then it certainly has been modded.
DO NOT try to connect it to the Internet because as soon as it connects, Nintendo will automatically push an upgrade that wipes out your modifications. At best, you won't be able to play the games you previously were playing. At worst, your Wii will be bricked.
Well, maybe things have changed, but I got my Wii about 4 years ago and a couple of years ago I thought it would be fun to connect it to the internet. Figured out how to do it and within 30 seconds of connecting, I lost all ability to play any of my games. Had to go down to the electronics shop and have them re-configure and roll back my machine.