Hi I have an Advent 3511 PC With a recent Gfx upgrade of an Nvidia 5950 Ultra Im now concerned that the power supply isnt up to the job. I get random lock ups when running gfx intensive games like BF2. My bios, drivers etc are all up to date. My problem is that instead of the usual power supply mount of 4 screws I only have 3 with one being in the middle of the right side. It may also be a different size. How do I go about getting the right power supply that will fit?