Lol yeah.
Screw motherboard into the case = 3 minutes
Thermal paste/CPU on motherboard = 2 minutes
screw in Harddrive, hook up sata = 2 minutes
Optical drive, if you even bother = 2 minutes
Install RAM = 1 minute
Video card into motherboard = 2 minutes
screw in power supply, plug everything in = 3 minutes (unless your a fag with a windowed case and LED lights, then you're probably gonna fuck with the cables for 45 minutes here)
And these times are conservative, in case you've got Parkinson's disease or some shit.