ok 1st un-install the graphics driver for the vga
shut-down the pc
plug in the g-card
boot up and go into BIOS, in the bios menu somewhere will be an option to disable the on-board VGA
disable it, then save and quit
now hopefully windows should boot
will will most likely find that the desktop is large and cluttered
now provided you get this far and you can see the screen you will now have to options
1 use the drivers that windows update will provide you with or 2 install the drivers that you have downloaded
you should then be prompted to reboot
once you have fully booted you should see what to be an almost normal desktop
all you should have left now is to tweak you settings to get you screen how you like it

i hope this helps you
good luck