Hard Drive Lag Spikes & Fuzzy Screen - Win8

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The last few days I've come across a strange problem. I ignored it at first as I thought it was just some kind of anomaly but it seems to be getting more frequent... It seems that my secondary drive is causing lag spikes in my system.

Yesterday In particular I was working off a bit of Matlab code from my secondary drive. Every 5 mins or so I'd hear the drive spin up. It's very subtle so I can't quite tell where it's coming from but I'm sure it's the drive. I opened up task manager and keep an eye on the graphs. Indeed every time there was a lag spike, my D: drive would hit 100%.

I'm not sure why it's happening, I've set power options to give 30mins idle before drives are shut down. The drive isn't fragmented at all, indexing and the usual stuff should be on default. I recently did a reformat about 2 weeks ago so everything should be running smooth.

I'm getting a second perhaps different issue but it seems to be quite frequent to the lag spikes... My screen fuzzes out randomly. Only for a split second that it's just about noticeable. I have no idea if they are related but I have no idea why this is happening.

My system:

AsRock Z77-ITX
i5 3570K @ 4.5GHz
Corsair H60
Corsair 8GB Vengeance 1866
Sapphire 7850 No overclock
Samsung 64GB Msata (C Drive)
WD Blue 320GB (D Drive)
400W silverstone 80+ Bronze PSU
Windows 8 Pro

This system has been running fine for the last 6 - 7 months at these clock speeds. I'm 99.9% sure it's not a overclock issue. The PSU should be fine, my system only draws about 300W at the wall on full CPU & GPU load. 

I have a feeling that it could be electrical noise of some kind. When my flatmate turned on the vaccume cleaner my screen went really fuzzy for a good half a second or so. Otherwise it's quite random and very quick ~10 - 20ms. I took an oscilloscope probe around my HDMI and PSU cables to see if I could catch some spikes. There are some big spikes on both those cables, especially when turning lights on and off, ect but they didn't seem to cause my screen to fuzz... 

These things too a while to capture, it would usally be when I left the scope armed and left it for a while. When I came back, a spike had been caught.

Spike on HDMI

Spike on HDMI

Spike on Power Cord when switching on light in the room

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Right I've gone and figured it out...

It was mains spikes that was causing the problem with my screen. It turns out that my flatmate upstairs has a european plug going into an english socket via an adaptor. Everytime she kicks the plug under her desk it gives off some sparking noises and hence sends some RF crap back down the line.

Now the chances of my monitor PSU not being able to filter that out is actually quite low due to all the filtering inside the switch mode supply. My HDMI cable however is tangled with my mains wires and there are none of those ferrite rings on it. When a spike comes down the mains, it couples to the HDMI cable and messes with my picture signal. As we saw in the spikes above.

There's not much I can do about this than maybe just shield the cable with some tin foil and tape perhapse. I might get a new one with ferrite rings on each end. Appart from that I've told my flatmate to stop kicking her plug... :P

I'm not sure if this explains the lag and HDD issue I'm having but I'll see during the next few days. Might do some more experiments and see what happens when the plug is wiggled duing computer useage.