Slow PC possibly hard drive issue?

[screappy]

I recently built up my first computer and It plays almost everything I throw at it at decent fps (Like BF4 on very high 60fps+).But I think that my hard drive is problematic,it keeps slowing down my PC suddenly(Like opening folders,different options,menus and right clicking folders),but in games I have no issues.And the weirdest thing is that everything is brand new.Is it really my hard drive or something else?And if it is what can I do to fix it?

My PC Specs:
CPU:AMD x4 760k
GPU:NVIDIA GTX 750 Ti StormX Edition
PSU:Corsair 430W
Motherboard:ASRock FM2A78M-HD+
HDD:Seagate Barracuda 500GB at 7200
RAM:4 GB
OS:Windows 7 64 Bit

 

[Mattios]

Try downloading this and see if it throws any problems http://www.seagate.com/gb/en/support/downloads/seatools/

 

[screappy]

I ran all tests and nothing seemed to be wrong,It just said "Passed" with a green color which I think is a good sign.I also ran "Fix All" option which also showed the "Passed" sign.

 

[screappy]

I would also like to mention that this "slow" doesn't always appear,It happens when I install something or download,even if it is something small like skype or a browser.And I'm almost sure that it isn't my processor since it doesn't go more than 2-15% usage while browsing or doing casual stuff.

 

[Mattios]

What does the 'disk' list in task manager show during these slow times? Show the values as percentages.

 

[screappy]

As I said it happens randomly,but I have noticed that every time I download big files my hard drive is working at 100% and the computer slows down.In task manager it says that utorrent is the case.I have tried bitcomet and other torrent downloaders but all have the same issue.I think it's because I have recently updated my internet and my hard drive can't work fast enough for the speed the files are downloaded.In utorrent used to say "Disk 100% overloaded" so I googled and found that this was common issue.I managed to fix it so it doesn't say that the disk is overloaded anymore,but my computer still slows down.