Дмитрий is totally right. And I've just wondered what you really wanted to know was the difference between だけど and だけれど? If so, they are semantically identical. The former is conversational informal and the latter is general one.

As far as I know, they are substantially identical. けれど is just a more formal version of けど, and you can't compare だけど and けど, because だ is just added after nouns and na-adjectives before けど.