I have bought an Acer Aspire 5755G 4-5 days ago (i5, 8 gb ram, 2 gb nvidia gt 540m)
I didn't have any problems al all ultillast night when a it started making a strange sound.
When I enter a game, the fan from the graphics board starts, and for a second when starting it makes a slow grinding noise, same thing when i exit the game and the fan stops, or slows down.
Also while playing the same fan makes some grinding sounds, from time to time.
I tryed holding the laptop in various positions thinking that's the problem, because it didn't happed from the start.
Please i don't know if i can solve this, or if i must send it back.