Windows 7: Fan runs crazy, track-pad crazy, browser hangs, slow & unresponsive

Hi All, I hope someone here can help me as I can't go on with this crazy machine any longer...

My machine is a 2012 Sony Vaio, I've just updated my system specs. What happens is the following:

The fan runs for no apparent reason. It just takes off, loud and blowing out hot air even though the machine is just ticking over, more noisy than it ever used to be. As I'm just writing this, it's racing away

The track-pad sticks and just generally plays up, I've attached two screenshots, the first as I was updating my system specs (writing specs or moving the pointer around, and it decides to highlight a load), the second as I was uploading that first screenshot (I was clicking on 'manage attachments'). Other times the pointer shoots around all over, no corelation to my hand movements, also when I go to tap the pad, the pointer flies off.

Comodo Dragon has been hanging, sticking, not-responding.

Generally my machine has been performing horribly, so I performed all the operations below but nothing has helped:

EAM runs its regular scans, every couple of days, finds nothing
MBAM finds nothing,
MBAR clean
SAS clean
Hitman Pro default, clean
Following Chiron's suggestions on TechSupportAlert:
Kaspersky TDSS Killer clean
Comodo Cleaning Essentials clean
Glary Utilities Pro default scan and fix
I then ran SFC /scannow and everything is fine,
Puran Defrag running a boot-time defrag
Full disk check
Carefully vacuumed the ventilation slots
Reinstalled (repaired) Comodo Dragon

Any suggestions massively appreciated, TIA

Work through the Troubleshooting Steps for Windows 7

Consider doing the superior Clean Reinstall - Factory OEM Windows 7

Great info Greg, exactly what I was hoping to find.

The areas I particularly want to better understnd are: HD Diagnostics, Core Temp, new Driver Install, Process Monitor, Event Viewer.

What a fantastic library of knowledge. Warmest thanks to you and Anak!

I'll post back anything that turns up, cheers Chig.