I have a secondary hard drive in my computer (500gb) and recently when moving files over to it, the speed will drop to 0 and then going to access the drive in My Computer comes up with "Could not be accessed due to I/O error" or something. I'll have to restart my computer and it'll work fine for a few minutes until I move files onto it. Sometimes I can move gigabytes at a time and it'll be fine, but mostly anything over 1mb stops it. I'm running Windows 8. Let me know if you need anything else.