My pc is acting weird! Help!

[Eyb0s]

Hello everyone I need help. So I bought first pc ever! I was ( and still am super happy), but It performs badly. So I have gigabit Internet. And whenever I download something through steam, torrent or anything else my hard drive acts weird. For 5minutes or so It writes fast I mean 200Mb/s. But after that It drops to 20Mb/s and then it literally eats my ram (24gb of them). Task manager shows 99-100% Ram usage, but does not show which program or task is using it.

And after I restart my pc around 24gb of file i was downloading is corrupted or just gone. I tried Seagate tool, sentinel tool but both show 100% health. 

 

My rig:

Intel 4690K 

Zotac 1080mini

Msi z97 gaming 5 Mobo

Hyper x fury 24gb 2400mhz ddr3

[Eyb0s]

1 minute ago, BlueScope819 said:

What model of hard drive do you have? This video here does a better job of explaining it than I could, so give this a watch.

 

Seagate st2000dl003-9vt166 HDD

I don't have money to buy ssd now.