Linux

Hi, I am a long time Windows user and recently try this Debian Wheezy OS. Burn Debian ISO in Windows environment and then select DVD ROM drive to boot first in BIOS.

The first installation of Debian (GNOME) was with multi-boot option that allows booting from hard disk and DVD drive. I then realise my BIOS was altered when the ACER Phoenix BIOS F2 button fails to response but there is the F12 button to select a unique multi-boot environment. I was then able to boot to FreeDOS to install a DOS environment which I then use to load a CD containing DOS BIOS which I then use to flash the ACER provided BIOS. My ACER Phoenix BIOS was restored. I still don't think Debian OS installation can actually alter my BIOS.

The second installallation of Debian (KDE) was only with hard disk booting option. I use ReFIND, hoping to boot to CentOS DVD but the Anaconda boot to command line interface and I don't know what to do do initiate the CentOS disc installation. I then use Live GParted to partition and format the hard disk, hoping the Grub 1.99 will be removed and my original BIOS restored. When I reboot, my BIOS F2 continue not to work with no multi-boot selection (F12) and then the BIOS shows "Operating System not found".

Is the BIOS altered to BIOS-UEFI?

what can I do now? Use my other computer to:-
Try to boot USB operating system?
Try to boot USB Grub?
Try to boot Phoenix Crisis (WINCRIS.exe)?

Hmmm.
I don't think a standard installation of Debian (or whatever distro, actually) can mess up your BIOS like that.
I believe that what you're trying to say here is that when you first boot with a Debian DVD, it allows you to "try" the operating system directly from the DVD before actually installing it in your hard drive.
Here's what I would do. When your computers starts, enter your BIOS and tell it to boot from the DVD drive or a USB stick, whatever media you have an operating system ready to boot. Then use the accompanying tools to reformat your hard drive, and install the operating system itself if you want to do it.
If you're a Windows user, I'd suggest you to take a look at the Linux USB Live Creator tool, which allows you to format an USB drive, install an image of some Linux distribution and make it bootable so you can use it as a LiveUSB to troubleshoot a computer or to install the operating system in your hard drive. Hope it helps.

The BIOS screen "Press <F2> to enter Setup" appears but when I press F2, nothing happens either and I ended up seeing "Operating System not found".

My Win7 or CentOS DVD doesn't load at all after seeing the BIOS screen. I tested the 2 discs on another computer and they can load after setting DVD-ROM drive as first priority.

See here for some alternate methods of entering your BIOS.
And here for BIOS recovery in an Acer laptop.
Hope it helps.

Linux will not reformat your BIOS.

UEFI may go bananas of its own volition, however.