Hello, I have read a lot of threads on this subject, often with many unsuccessful procedures and checks advised. I have two hard drives, both 200gb, two dvd drives, all this has been working correctly until one night when I was doing lots on the computer, it froze and corrupted the hard drive (C) which now has a few unreadable sectors but can be used to store files. I have since installed the operating system on (D) as the OS on C kept running into problems. Since setting up the computer (again!!) I wanted to install the card reader which had vanished from windows explorer (usually displayed as 4 drives) So I unplugged the three cables from the motherboard (USB, Firewire etc) that were in the back of the card reader. At the same time I installed a PCI fan to give extra cooling. When I now start the computer I get INSERT SYSTEM DISK - PRESS ENTER. It wont boot off CD or the hard drive. If I unplug one of the hard drives, the CD will boot. I installed windows back on the C drive then on reboot plugged the other hard drive back in and had a choice of operating systems, so I booted the D drive and wiped off the XP setup files on C drive. All was well until I left the computer on and came back to "boot priorities have changed" then the INSERT SYSTEM DISK - PRESS ENTER" problem again. If I boot from CD I can see the directory of the D drive so access is not a problem, all drives are detected on startup, I have checked all connections and I have everything set ok in BIOS I think! Any ideas?