This build was bought by my parents 3-4 months ago
Yeah the monitor says it cant detect any display signalAnd it's been working okay until now ?
I mostly think the cpu is broken since it just turns on but the system cant detect any display signal plus its cold in my place right now and i saw some droplets building up in the heatsink and the cpu fans when i opened the caseiGPUs rarely develop any faults.
The only suspect item in your specs list is that Boston PSU --- basically it's cheap rubbish, that's why the builder has fitted the 750w model to try and compensate for it's poor quality, when in truth that system doesn't need anything like 750w. A good quality EVGA or Corsair 500w PSU makes much more sense.
However, before replacing the PSU, try replacing the monitor's signal cable first as obviously that's much cheaper and might just do the trick.
That's all I can think of at this time.
The psu is not the prob since the fans are spinning and it lights up so psu out of the question but im probably gonna replace it sooner or later before it turns itself into a homemade c4.Does your computer switches on at all? Fans are spinning? Are you see drive activity/blinking lights/sound?
Did you tried to reseat display cable? In both ends. Are display itself works?
Otherwise I agree with a guy above about Boston PSU as primary suspect. Another rebadged dumpster dive find where 750W most likely is group regulated 450W (barely).