One thing you fail to make clear - and I am confused by the reference to USB in your OP - is if this Seagate HD is the main interrnal drive or if it is a USB connected external one.
The fact that it has failed both the short and the long test suggests that this drive is on its last legs.
If it is your internal C:\ drive, then you need to get your data copied off it ASAP. You can do this in 'Safe mode', Windows Explorer works in safe mode. You will need enough external storage to hold all the data you want to salvage. By this I mean things like your work, photos, music, videos and everything else that tends to get forgotten - things like contact lists, browser bookmarks and any registration codes you have for software that you may have downloaded. Then you will need to buy another drive and re-install your OS, presumably Win 7 from the date, then all your applications, and then you can put your data back in.
If it is an external drive, then stop using it until you can get a replacement and then copy your data off it.
Do not apply any more tests to this drive until after you have got your data off it. These tests can stress a failing drive to the point where it dies. Once you have your data safely copied, then you can go back to investigating problems with this drive - but back-up your data first. If it is the internal drive, then it is nearly five years old which is not a bad lifespan for a hard drive.