Dear Max90, I just experienced the same problem with my M1530's Fan after booting to Win7.
I recently took apart my laptop to clean the dust and pulled the fan apart to clean out the blades.
When I press F2 to start the setup the Fan will continue to run even in the Desktop.
Again I have the same problem, fan starts on Bios A12 screen, then the fan shuts off on the Desktop. If I press F2, do nothing in Bios, it will run in Desktop.
Good Luck