In addition to what the guy's said.
If you dont have another pc to try it on,try this,turn off the computer, disconnect the power cord from the back of the computer, disconnect the power cables from the backs of all of the drives(CD-ROM, DVD-ROM, CD-RW, floppy, hard drives) except the boot drive(it has the Windows O/S on it), remove all cards that are inserted in the motherboard except the video card(it has the monitor connected to it), reconnect the power cord, and turn the computer on.
If it doesnt artifact then as the guys said it is your PSU.