How can I override fan cpu warning on startup?

I have a Dell 5100C desktop, in which the fan was faulty. I replaced it with a generic fan of an equivalent speed (2500 rpm), but the difference is that this is a two wire fan, while the dell one was four. It works just fine; I spliced the red and black wires to the old connection, but I lack the two ‘smart’ wires that controlled the old fan speed at various temperatures. My assumption would be that the new fan will just run at the top speed all the time, and that is fine with me, as I’m not bothered by the noise. I’ve been monitoring the hard drive temperature with free software, and all things appear normal (in fact, better than before) and I’m relatively certain everything is being cooled adequately. My problem: Now that I’m lacking those two wires, the computer thinks there is no fan. So, when I turn it on, I receive an error message ‘CPU fan warning’. In the bios, there is no ignore feature to be found. Of course, I can press F1 to continue, but I would really like not to have to do this everytime I boot up the computer. Any ideas? Thanks!