Well I have doen near a hundred virus scans on my pc (over time), and it says I don't have one threat. But when the OS was on the 500GB, it crashed, formatted many times, it just did the same. Formatted it, and loaded my 2TB, and now it does the same thing? Even though there is not even one program using the 500GB, could it still rash my pc?
There doesn't specifically have to be a program using it in the foreground.
A background service (such as defrag or indexing) could be accessing it and still having issues.
I would scan your drive(s) with the manufacturer tools (e.g. SeaTools for SeaGate and Data Lifeguard for WD drives) to see if SMART is alright as well as if there any other other diagnostic issues it can find.