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)?