Trouble with CHKDSK. After running and perhaps deleting, computer lags

Hello, for the past 2 days my computer would run CHKDSK at startup. At first I let it run not knowing what it is (I'm not adept in computers). Apparently it deleted something on the first day. The second day, CHKDSK started up again and it, I believe, deleted some more stuffs.

Now during this second day, my computer started to lag and freezes up despite whatever I was doing: browsing, gaming, even while I was backing up some files. It was to a point where I would need to shutdown my computer or restart it by using the buttons on the machine instead of going to the start menu. I also had a blue screen once saying "KERNAL_DATA_INPAGE_ERROR_".

I've tried looking up for solutions. I first assumed I had some virus so I used Microsoft Essentials, AVG, S&D and Ad-Aware. I used AVG in safe mode too. None of them detected anything. I also tried sfc (I attached the log with this post, don't know how to do it in txt sorry). After CHKDSK ran, I tried "fsutil dirty query c" and it says it was not dirty. However my computer lagged and eventually forces me to shut it down.

At the end I stumbled on Startup Repair and just ran that. After over an hour it seems that did the trick and right now my computer seems to run fine, no lag, no freezes, games work too however CHKDSK still runs at startup (which I cancelled because I was afraid it would delete something again and make my comp unusable again). This time I tried "fsutil dirty query c" again and it says it's dirty. But my computer seems to be fine despite that. So my question is, should I just turn off CHKDSK and leave it at that (leaving it "dirty")? I don't really understand the consequences of it being "dirty" but my computer seems to run fine. Or is there another problem I do not know.

Specs:
Windows 7 Home Premium 64 bit
i7-2600 CPU @ 3.40GHz 3.40 GHz
8GB RAM

Try running the disk manufacturer diagnostics tool, i think the disk is on its way out.