What is the HDD Led Connector For?

Not at all.
That LED indicator only tells you that the hard drive is working - that data is being transferred.
Perhaps you need to do a good anti-virus / malware scan to make sure that you don't have any infections.
If you have had the system a good long while, then perhaps it is time for a re-install of Windows.
Works wonders for a slow pc.
 
Hi, thing is that yesterday i installed a hyper 212 evo and after that i can't get to my desktop without it crashing on me. I was checking connections and saw that that thing wasn't plugged in. I believe it is the hard drive because the cpu and gpu did well in a stress test I did before my system crashed. I have a core i5 2500k a hd 7950 a p8p67 a tx750 psu 8gigs of corsair ballostix sport and this is my hdd
https://www.amazon.com/gp/aw/d/B000I0R91K/ref=ya_aw_od_pi?ie=UTF8&psc=1