Radeon HD 6670 issues live DVD

Hello,
I'm not able to install Zorin OS because of Radeon HD card ?
First things, first:
Zorin OS 6 OS 6 Ultimate 32bit from dvd (checksum ok) Live dvd created with ImgBurn (on my desktop and notebook Dell Vostro3540).
My PC: desktop, homebrew, 4 Gb Ram, Intel Core 2 cpu 6600@2,40 GHz, AMD Radeon HD 6670 graphic card. MS Vista 32 bit Business
Installation process:
A lot artefacts on screen during Zorin live sesion, crashes reports. The same when I chose the safe graphic mode. I've tried the live DVDs with Ubuntu 12.04 and Mint 14 - the same problem, even on much larger scale, I can't see the desktop properly.
Installation (to be sure) on Dell notebook (Intel graphic) was nice and easy.
What should I do? Need advice and help Thanks in advance

Thanks Swarfendor437!

My motherbord is:
Gigabyte GA-G41M-Combo
Intel G41/ICH/rev.2.0
Socket 775/PCI-Ex 16/Micro ATX
2 DDR3 2-CH/HD Audio
GbE LAN/4 SATA 3GB/s/8 USB 2.0

In BIOS I found something like:
Advanced Chipset setup -
Onboard VGA :
"Enable if No Ext PEG" (default)
"Always enable" as manual says: "Always activate the onboard graphics, whether or not a PCI Express card is installed"
Init Displays First
PCI or Onboard or PEG

It's working now! What should I do next? After installation?

hi swarfendor437

I new for Zorin,
i understand your Answer. but my M/B not have vga on-broad.
spec my PC
cpu AMD fx8350
m/b gigabyte GA-990FXA-UD5
vga redeon hd 6970
ram 16 Gb

how to install driver vga and M/B driver
I should do ?

Best

thank so much.

Thank so much, swarfendor437

This s work for vga and sound card.
I test Zorin and I like it.
its a good begin for Linux.

thank