Is there any reason why a non-system disk would cause a machine to NOT boot up? Freezes at the splash screen stage. Remove the disk and it boots fine. Thanks! "Storage disk Freezes Boot"

The second disk may be dead or if IDE type, you may have the jumpers set wrong. IDE requires that when two drives are connected to the same cable one must be set as Master and the other as Slave. Second option is to set BOTH to CS (cable select). Master/Slave allows either drive to be connected to either connector. When using CS the drive connected to the END connector will be the Master.

NO: The disk was working OK before, just disconnected it from the power supply to do an upgrade. No jumpers etc were reset. The disk also works fine with an alternate boot system, other disks on the same system works fine on the upgraded architecture.