Firstly, upgrade your power supply asap. Too low a power supply can seriously damage your hardware like that Pentium 4 you have in there, and your snazzy new video card too. Have you ever played Sim City 4? If so did you ever turn the power down on the power plants? If you did you would have found that their life span shortened considerably.
Second, how many drivers have you tried exactly? I would head over to
www.guru3d.com and take a look at their Nvidia section of forums, they have official and unofficial drivers available there too so there are loads for you to try. The site specialises in all things video card but they also dabble in overclocking and general hardware too.
But definately sort that power supply out!
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