Not quite sure I can blame Windows for this one but Windows makes a good scapegoat. In short, when I reboot from Windows back into OS X, the external Firewire drive is not detected. System Profiler shows it as an unknown device; I typically have to unplug the power on the disk and plug it back in. This is on a 27" 2010 iMac & I'm using the external drive for Time Machine and general data (it has two partitions); I'm not booting any OS off it. TL;DR I have a Seagate FreeAgent GoFlex Desk external drive using the at Firewire 800 base. Studying Seagate's forums and Google results in general, folks have wildly mixed experiences with this drive. My experience has been generally decent on the OS X side but Windows has added a new headache. The drive likes to spin down and go to sleep, even in OS X. I use it with Time Machine so the drive wakes up and does its thing & has little time to sleep. (And I'm not using Seagate's software in either OS X or Windows because of seriously headaches others have had with it.) Upon booting into Windows the drive is seen and alive for a bit but eventually goes to sleep because I don't really use it there (its partitions are read-only in Windows). If I reboot into OS X while the drive is resting, it simply doesn't get detected. System Profile claims "unknown device" in the Firewire section and I have to hard reset the thing -- by re-plugging its power -- to get it noticed again. FWIW I've never had this issue between subsequent reboots of OS X (likely because its never has much time to sleep). Any ideas? I guess I could explicitly try waking the drive up in Windows before rebooting to OS X. It's a kludge but kludge is Windows' middle name, IMO.