It's not unusual for a CMOS memory reset to spontaneously occur when a system is worked on, possibly provoked by an unnoticed static discharge.
In most BIOS you find one or more of 3 common options. In the screen which shows detected drives, along with SATA and IDE channels you may see a FDD drive type (eg 3.5" 1.44MB) which can be changed to an option such as Not Present or Disabled. Sometimes in a section like Onboard Peripherals there is an option to disable the onboard FDD controller. Also somewhere you might find an option such as Enable FDD Seek at Boot. If this exists and is set, in some BIOS the seek will still occur to test the drive, even if the FDD status is currently set as Not Present in the equipment list, so disable it.
Edited by Platypus, 05 January 2015 - 09:22 PM.