I put in Super Mario Galaxy 2 in my Wii, it didn't make that noise when the disc drive starts up, it just sounds like as if it stalled. As soon as I started the disc channel, it immediatly said,'An error has occurred. Remove the game disc and power the wii off,' or something like that. Why does it happen? Same thing happened with 007 Quantum of Solace.

Make sure discs aren't scratched or dirty, and they're being inserted the correct way round (I know it sounds obvious, but you gotta check everything). Other than that, not too many ideas I'm afraid. Assuming you have homebrew, you could always try loading the discs with Gecko OS or something, but this sounds more like a hardware issue than a software one I'm afraid.