Only took us just over an hour...
Vague process for those interested:
Chipset drivers updated (not too sure whether this was done or not as per recommendation
)
PC bluescreened due to invalid configuration in Windows boot file. (not too sure whether this was because the RAM had been set to 256MB, or whether it had been set to dual processor)
Created USB Windows installation media as system could not get to F8 Advanced Boot Options
Booted from USB, went to command prompt
Typed in these commands:
bcdedit /deletevalue {default} numproc ---> Reset number of processors
bcdedit /deletevalue {default} truncatememory ---> Reset memory limit (removed it)
scf /scannow ---> Scans system files, checks if they're corrupted, attempts repair and local cache
System was then rebooted, went into Windows, and all 4 threads of the i3-2100 chip were visible in Windows.
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