Why won't my xbox 360 run COD MW2?

I have the original 360, and whenever I put in MW2 the disc is unreadable message pops up after 20 seconds or so. This rarely happens with my other games. I tried a friends copy and the same message came up, but it worked fine on his xbox. Both discs are pretty much brand new, so there are no scratches on either of them. I went through the microsoft support website, and it obviously didn't help at all. I tried running it without the 15 GB hard drive (ya I know it sucks), and the same thing happened. I moved my xbox, cleared the cache, and nothing worked. I even installed it to hard drive, but it tells me to re install the game. I don't know whats wrong, I've tried every thing that I've read. Does anybody please know anyway that I could fix this problem, without having to send it to freakin microsoft, or by buying a new xbox?