Hi newcomer and welcome to the Tom's hardware forum.
1- What is the configuration of ur PC? That means that the person want know what components (CPU, mobo, RAM, GPU, etc...) do u have installed in ur rig.
For my are this:
CPU: Phenom II X4 955 @ 3.8GHz
Mobo: Gigabyte 890FXA-UD5
RAM: Crucial Ballistix Tracer 4GB (2x2GB) 1600
HDD: 2x500GB Itachi
Cooler: Hyper 212+
OS: Win 7 Ultimate x64
and other things like the case, monitor, speakers, keyboard, mice...
2- What is desktop? See answer here
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