Apple seems to have traced the problem that reportedly caused some first-generation MacBook Pros to make a whining sound when used.

One Mac user is reporting that Apple is replacing the logic board in some (though not all) machines. The new board requires Mac OS X 10.4.6, not the Mac OS X 10.4.5 installation that the Mac shipped with.

"I can hear no whine whatsoever, whether running on AC power or the battery," the user reports on the MacInTouch forums.