Switching back to onboard gpu?

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http://askubuntu.com – I have been getting constant freezing issues whenever I am running videos. I know it is not a driver issue as I was having the same problems when running windows. I want to move back to my onboard gpu and take out the card I have. However, every time I do this (Unplug the gpu and hook the monitor up to the mobo) the computer doesn't turn on. I'm pretty new to all this stuff so any help would be appreciated =] Thank you! Graphics Card: BFG BFGEGTX275896OCE GeForce GTX 275 OverClocked Video Card - 896MB, PCI Express 2.0 x16, SLI Ready, (dual Link) Dual DVI, HDTV, HDMI (w/ Adapter) MOBO: AS (HowTos)