Didn't really see much posted here on this, but wanted to pass on a fix for Vostro 420 owners. Installed Windows 7, updated BIOS from 1.14 to 1..23 and suddenly started noticing a very high pitched buzzing noise, which seemed like a power saver issue in the BIOS. Strangely, every time I would plug or unplug and USB devices, the noise would stop for awhile then start again. The only fix I found was to plug my iPhone into the PC and it would stop. Finally, I decided to go back to 1.1.14 and the noise is gone, without having to plug in my iPhone.
Nothing major, just hoping to save someone some hassle.