I've been confused by this for about 3 months now, I hope I'm overlooking something simple, but I don't think I am. I have an Acer Aspire One (D250-1197) with Windows 7 Starter and I hear a noise which sounds to me like the hard drive is spinning up (almost more sounds like a cd/dvd rom revving up). It does this at seemingly random times, I was watching a movie a couple days ago on the tv and had the netbook in front of me and kept track of the times it made that noise - 10 times in an hour and a half. I am pretty certain its the hard drive because, well, nothing else in the machine spins, and the hd activity light comes on immediately after I hear the noise. Now, I have tried to watch what is going on through task manager and I have not noticed any pattern (actually nothing consistently spikes cpu usage at all). So after not noticing anything in task manager I tried resource monitor and looked at the disk activity - again nothing stick out. I've watched both of those things for probably an hour over various days attempting to figure this out. I considered that (with the thoughts of Rick in IRC) potentially the netbook has some hardware/bios level control over the hard drive to conserve battery. I don't believe that is the case because I have a dual boot set up with Ubuntu 8.04 and do not have the 'spin up' issue in Ubuntu. The reason I've called it a 'spin up' with quotes is I don't believe the hard drive ever shuts down, I never hear the classic noise you expect to hear from a hard drive shutting down. I was also watching the NCAA basketball tournament games tonight and I heard it do it, streaming the games should keep some I/O going to the HD so it should never shut down. I've of course checked the power management settings to tell the drive not to shut down. My girlfriend also has the same netbook with Win 7 Starter and her's does it too, although it doesn't seem as frequent. Another random thought is that the issue still occurs in safe mode..