Methinks the diagnosis is drifting towards Hardware failure in the form of Hard Drive problems. Ideally if you have another PC capable of burning a disk you would download and burn to disk Seatools for DOS
http
/www.seagate.com/support/internal-hard-drives/consumer-electronics/ld25-series/seatools-dos-master/
This would create a bootable disk capable of checking out the functionality of your Hard Drive.
If this is not possible, contact your Vendor with a view to returning the unit for repair.
Meanwhile once you get up-and-running be sure to create
1. Repair Disk
2. System Image
This can be achieved by typing 'Recovery' at your Start Screen, and from Settings choose Windows 7 File Recovery. This screen contains links to both the above. Ideally create on USB Flash drives (Too many failures on DVDs!)
One other possibility is a failed RAM stick, this could be checked by removing one stick at a time to see if matters improve, (but don't void your Warranty by breaking any seals to remove RAM (Unlikely, but just-in-case...)