Thanks for the advice using a wooden spoon, but the noise is more like a low pitch vibrating hum, sorry for the bad explanation. I think it is the ballast fan. I had a PC Case fan go out a couple of years ago that made the same type of noise.
A quick slap on the case just after power up and that fan would get quiet until the next cold boot...replaced fan no more noise on my PC. How do I find an a diagram and or instructions to get to the fan and exchange it?

RBK, June 2009