I was Told by the Hp engineer that i cannot anyhow upgrade my graphic card by plugging in to a branded computer .. Is this true?
Sorry -- CPU, PSU (so many acronyms, so little time).
Perhaps the heat and space issues were what the HP guy was warning you about ?
I notice the AirFlow By the fan of the psu Actually sucks in air to the interior of the casing and hence blow hot air inside . The heat would then clog up the whole casing and it would feel very hot just by touching the casing .Opening the case isn't always a good idea because the airflow will be different. For example, the PSU fan will only serve the PSU not the components inside the case.
Have a look at the layout as a whole and apply common sense.