You're going to need the means of wiring the system to your vehicle's electrical system.
You're also going to need the appropriate cables to connect the system to your audio system.
And since it wasn't listed in the ad, you may need software. Most of us recommend a front-end, since it will give you driver-friendly access to any/all functions you want from the PC.
Search through the forums here to see what front-end options are available. Some are free. Others are not. Some include GPS map data. Some use "download on the fly" or cached maps from a system like Google Earth.
I have to ask, though...
If you purchased a PC for your ride, you obviously have some functionality in mind.
That means you bought this unit with that functionality in mind, yet you didn't bother to do any research about it before you clicked BUY IT NOW.
I'll tell you this. If you're looking for zippy performance from that PC, you're going to be SORELY disappointed. The Via C3 processor in that motherboard is the equivilant of a higher-end Pentium III in most respects. Thr4owing 1GB of RAM at it will help performance, but only so much.
Will it handle media playback and GPS and OBD connectivity and all the common functionality that most users desire from a vehicle PC? Yes, it will.
If you want to play videos or see pretty 3D visualizations on the screen, this system may not be up to snuff.