b kilburn

i have just downloaded imgburn. I want to change blu-ray discs (on my hard drive) to iso files mainly so I can use media center to play them through power dvd which it won't do unless they are iso's. I ran img burn on one and it seemed to create an iso file called rar archive. I have winrar 3.7 on my pc but I can't extract anything from the archive (even though it says it is 27gb) so I can't play it in any way. I don't really want an rar archive file so am I doing something wrong here.