BSOD when playing most games, some exceptions

The Key in use is the infamous Lenovo Stolen Key - which leaked even before Windows 7 launched, and was recalled from all sources. It has never been legally used on ANY computer.

The Key is of the OEM_SLP type - which requires that the motherboard have a matching SLIC table with the manufacturer's own certificate to allow self-activation of the OS on every boot.
Retail motherboard do not and cannot have such a SLIC table.
Your motherboard is a retail one.

The installation has been enabled by use of a hacker's Activation Exploit, and is therefore counterfeit by definition.

If this Key is in use it your father's place of work, then all such installations are counterfeit.

This is NOT an upgrade - it is NOT a case of 'missing files' - it is piracy, pure and simple.

The only safe option when an Activation Exploit has been found is a reformat and reinstall - it hooks into the OS at a very low level, and often carries unwanted guests with it - and can leave the system vulnerable to attack though backdoors, etc.

It's theoretically possible to do a repair install and fix it - but there may still be unknown settings and files present.

To reduce the cost - do you *really* need Ultimate edition? Why?
You almost certainly only need Pro at most, and more likely Home Premium.
Compare Windows 7 - Microsoft Windows

Why do you need Ultimate?
Are you using Bitlocker, or multiple languages? if not then you do NOT need Ultimate.

That's the worst possible reason for buying anything - but it's your money.