windows 7 - Computer does not boot from optical drive or from USB

I had dualboot of Windows 7 + Ubuntu 12 on an ASUS laptop.
Yesterday I triggered reset to factory settings through Windows, without realizing that I need to get rid of Ubuntu and grub first.

Now the computer is stuck with the following message:

error: no such partition
grub rescue >

The problem is that I cannot boot the computer with boot repair disk on a USB, nor from backup DVDs from this laptop.

I already set the "Boot device priority" to "Removable device" first, and then "CD/DVD" but it's still the same. It does not read either of those.

Is there any other way to force boot-loading the live USB / recovery DVD?

Thanks!