I'll try 3dmark.
So I tried 3dmark and there was a hiss, however even in its most intense parts of the test, I had to really listen for it. Nowhere near as loud as scrolling a particular few gif files on some of the websites I visit.
Odd, well do you have a CRT monitor or an LCD? I know a CRT can make strange noises when its a bit old... Could also be the PSU, IMO that is probably what it most likely is.
LCD, brand new. I tried an older monitor and a couple tvs just to be sure. I might have an extra psu laying around to try, if I can find it.