The original harddrive in my x51 was damaged so I had to get a new one. I bought this very similar one (http://www.newegg.com/Product/Product.aspx?Item=N82E16822236339) from newegg. However everytime I install the harddrive i get a message on the screen saying "Internal Hard disk drive not found to resolver this issue, try to reseat the drive. No bootable devices." Me thinking it was the new hard drive that was also messed up, asked for a replacement from newegg. Which they did accept and sent another one. But again i got the same message. I forgot to mention that when I install the old (broken) hard drive, it seems to work but again its broken so I have no use for it. At this point I think Alienware x51s have to have one certain type of HDD from dell or something like that. Please help!