I have an older Dell Optiplex GX620 with a Pentium 4. I recently purchased a new graphics card as the Intel Integrated Graphics did not have enough power. I purchased a PNY GeForce GT 620 card. When I tried to put the card in the PCI-Express slot, what I assume is, a resistor blocked the card from going in the slot completely as the graphics heatsink was in the way. I removed 3 of the 4 screws holding the heatsink in and pivoted it, this allowed the card the go into the slot. When I boot it though (I am running Ubuntu 12.04, which was running fine before with the integrated graphics) it goes through the initial BIOS loading screen, gives me the plain Ubuntu purple screen with no loading thing. Then the screen goes black and I get a "No Signal" message from my monitor. I have tried sort of taping the heatsink down, as I believed it to be overheating, but this did not help. I know that does sound a bit stupid though. Any ideas people have would be great.