PC component's power consumption

[Pandiani]

Hello people,
I need your opinions about following problem.
I have bought new graphics card. In its documentation I found that it requires 400 W power supply. My power supply unit is about 350 W. When I start a movie in windows media player (movie is on hard drive), computer restarts, but when I play games (many of them have great requirements such as CPU GHz, hard drive pace and simular) nothing happens. My question is:
does playing video require more power than new game? At first I thought that hard drive is bigger consumer, so when I start playing movie from hard disk, power lack cause system's restarts, but how to know for sure if this is true.
Do you know which components require more power?
Also if a video file is played from hard disk, is there more hdd activity than when I play game?
I know I'll probably correct problem when I buy stronger power supply, but I need to explain myself hoe it is possible computer to restart when plying movie and not when playing games. Which is bigger consumer, graphics card or hard drive?
Thanks

 

[brinks]

Video card uses more power than the hard drive.

 

[Pandiani]

I thought so, so this thing about reboots when playing video file is unlikely to have anything common with lack of power. If power supply unit is problem, than reboots will occur during games, unless more power is drawn when playing video file which is unlikely...