Suddenly one of my hard drives (E: so not the boot drive) started behaving oddly and suddenly becam inaccessible. So I tried to format it. Rebooted and the computer would not start. So I took the drive out and put it in an external enclosure and connected via USB and it works a treat. Put a new HD into the same SATA channel and that is doing the same thing. had to disconnect it to get the PC to boot up. Do you think it is the mother board? It is fairly new Asus PQ5 Pro Turbo. When I installed the mother board the device manager does not recognize the on board LAN. (shown as enabled in the BIOS) I can live with that but it it also has a faulty serial connection I am going to complain but before I do anyone any suggestions for things to check?