>>314780980A free PC is great value regardless of quality.
However.
As a rule Prebuilts aren't, be very, very careful with pre-builts.
Common things are:
Underpowered garbage PSU's made of old chinese newspaper and scrap metal.
Shitty dirt cheap MOBOs that usually gimp the hardware plugged in.
Putting a stick of decent RAM in with whatever they had lying around. Ending up with some weird number like 12/6/18GB and all sticks running at the speed of the lowest component.
The Idea being they put half decent shit that people will look at eg. GPU, CPU, RAM. Then put in the absolute shittest components around it and price it the same price point as other PC's using those GPU/CPU/RAM so at a glance it looks like agood deal, but in reality is a vastly inferior machine.
Basically if they won't name every component don't buy it. If they do, look up every single part and check it out. Rebuild the system in a system builder etc.
It's your money, do what you will.
But as a rule, it's better to build yourself.