Reboot and select proper Boot service or Insert Boot media in selected Boot device end press a key

[Chanel1234]

When I switch my Acer desktop computer on this keeps displaying on the screen when I try to start it up.

I have researched on the internet about boots and rearranging boots and such but mine looks a lot different that others.

When I press F7 to go to the Boot Menu, it asks me 'Please select boot device' between these two choices:

P4:HL-DT-ST DVDRAM GH24NS90
And
Realtek PXE B02 D00

When I press Del to go to settings,
I have tried changing the boot priority but the only options I have are:

Network:Realtek PXE B02 D00
CD/DVD: HL-DT-ST DVDRAM GH24NS90

Hard disk
UEFI
USB floppy
USB CD/DVD
USB Hard Disk
USB KEY

Which one should I choose? How can I stop these two error messages from displaying?

 

[CountMike]

Is there an OS on HDD ???

 

[helpstar]

hard disk
maybe your hard disk is failing
try booting with an install media for windows and repair windows from there if possible

Does your hard drive show up in BIOS anywhere ?

Which Acer model is it exactly?