Hi , My system is a Dell 518 Inspiron Dual Core E8400 CPU at 3GHZ, LGA 775 Mobo (Dell 0K068D-model). The question that I have is that I have purchased a used stock Dell Vostro CP825 CPU Fan 4pin two days ago, since my old stock fan made a humming / buzz noise (quite loud), with an error code of incorrect speed in dell diagnostics. The new used one was fine and quiet for two days since install, diagnostics checked no problems or errors. I now started hearing that same buzz noise though not as loud and not all the time (hearing the buzzing) but that incorrect error code is back. Could it be the used CPU fan is going bad since it was fine and two days later it starts making that noise and the error code of incorrect fan speed is back. Any advice would be greatly appreciated. Thanks