To disable on-board devices you need to be into the BIOS setup, not Windows in safe or any other mode.
To get into the BIOS you usually hold down the DEL key as soon as you power-on, and keep it pressed until the blue BIOS setup screen appears. If DEL doesn't do it, try F1 or some other F key. When in the BIOS category page, highlight "Integrated Peripherals" then press Enter to open that page. You should see an entry for 'on-board video' - press 'Page Up' or 'Page Down' key till it says 'Disabled'. Press 'Esc' key to get back to main category page - then press F10 (usually) to save and exit. If you get a prompt "Save and Exit (Y/N)?", be sure to press the 'Y'then press ENTER. PC will re-boot. You may have to remove and re-install drivers for new card AFTER making sure that integrated video driver is uninstalled from device manager first.
When turning the computer on I get a series of beeps. One long and 2 short and the computer doesn't boot up. For my Bios that is the beep code for a problem with the on board graphics. I have talked with emachines support and they had me unplug and re seat every thing that could be re-seated. I was then instructed to get a new graphics card. I bought a new readon 9250 graphics card and installed it. I get the same beeps and the computer continues to not boot up. I can not get any kind of screen on the monitor and it seems as though I can not enter safe mode to disable the on board graphics. Any clue as to what I should try? Any help would be greatly appreciated. By the way I should mention that this problem occured then after a week all of sudden and then some one powered down my computer and it went back to the beeps and no booting up.

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