I have never upgraded my motherboard since I have bought from store so my question is whether lenovo thinkcentre m91p series have atx or btx type of motherboard .moreover I would like to change my case which is the best case for atx type and a best psu for that case .I am thinking about to take cooler Master elite 500 and 350w corsair psu .I don'the have any graphic card over there ..... please,.....please .....help me friends. THANK YOU VERY MUCH.I like this forum. Thumbs up for this forum because I get correct answer from this forum.thankyou