No matter what OS you have, DRAMAtical Murder was made for all windows from XP to 7 so there's no problem there. To download the game you just have to go to this thread: In that thread you'll find many posts with links to download the game. To download it just click the links and you'll get to the download site where you usually have to wait a few seconds before the download button appears, then you just save them in your computer and once you have all the parts of the download you can install the game. If you read my post (the second one on the thread) you'll find instructions on how to install the game after you download it.
Dramatical Murder (ドラマティカル マーダー, Doramatikaru Mādā, stylized as DRAMAtical Murder) is a Japanese BL visual novel developed and published by Nitro+chiral. It was originally released on March 23, 2012 for Windows PCs as a first press edition, with a regular edition released on April 27, 2012.