Virus_3.1.exe
New Member
Is building a computer cheaper than buying one? 
^ Not to mention, pre-built ones often use poor quality components, especially the two most important ones. (Mobo and PSU)
The mobo will be the biggest difference in them, because a good one in a parts-built machine will have a lot more features, much higher build quality, and an unlocked BIOS. The PSU is a close second because the ones in OEM machines typically are awful, and if you build a machine you can pick a good one.