Pushed under the mobo two right size soft rubber bushes to save the PCB from bending & accidental breaking by laying the PC flat on a table. When started, DISK BOOT FAILURE....message came up. Was also not identifying the two HDs.

One HD is IDE type which is slave to a DVD-RW. Unplugged their power supply & restarted. The PC started working!

Can anyone please explain why it failed first & then worked. Also, a bit later after running, a 'switching off' sound is regularly heard from the location of the IDE units. Why this sound; also how can I restore both units without disrupting the 'peace of mind' of the PC.