If your PC is vibrating its something mechanical. A cooling fan, the hard drive (if its not an SSD) or an optical drive. At the very least take the side cover off and do a visual inspection for dust buildup and any blocked fans. Your PC will boot up into the BIOS screen without a hard drive or optical drive connected. Unplugging case fans for testing isn't going to make it blow up either, especially with the side cover off. If your motherboard has onboard video you could remove your GT230 and see if the noise/vibration goes away. If you are worried about further damage to your PC only turn it on for short periods or take it to a repair shop.