I'm used to putting my desktop on the floor. I know from periodic cleaning of my older machines that a lot of dust can get sucked into the fans. I just got a brand new machine and am wondering if it's better off on the table, or if there's some other way to minimize dust collection. This machine was completely silent the first few weeks in operation, now it's got a slight whirring when it runs. How long should I wait before I break it open to clean things out?