I have x51 r2 and recently (two months) it would lock up or restart its self and I will get the error message "Internal hard drive not found. To resolve this issue, try to reseat the drive!" I have removed the hard drive and reseated, unplugged cables and replugged. Used a Seagate Barracuda drive from another Dell computer and computer didn't recognize it. Nothing I have tried has any noticeable affect. May go two days without error or go two hours with two errors. Any advice would be greatly appreciated.