Hard drive makers have diagnostic tools. Seatools is what seagate uses.
I would like to point out some of the tests fail(Drive self test short for instance) even with the hardware working. Why? they have not updated the software in a while. Just do NOT use anything that writes ZEROs to the drive as that will erase it.
http://www.seagate.com/support/downloads/seatools/
This drive was just fine
http://img155.imageshack.us/img155/5094/seatools.jpg
You can also use HDtune(2.55, pro is not needed for this. and NEVER scan an SSD this way) as it has a surface scan option it takes quite a while.
http://www.hdtune.com/download.html
On that topic. Any time the hard drive is working hard and windows needs to access it, things can be slow. In fact if I push data from a SSD to my hard drive(keep in mind its a slower 5900 rpm seagate LP), it can grind that thing to a halt(even to the point that music playing off the hard drive can skip.). The drive only has one arm holding all the heads so it can only be one place at a time.