Computer refuses to shut off unless I unplug it

[raytre]

I replaced my hard drive with a Western Digital 500G. It ran great for a week. Then I booted up one day and the HD wouldn't boot up. I had power to other parts of the computer,fans and etc. When I tried to shut down by depressing and holding the power button it wouldn't shut off even after a couple of minutes. I had to unplug the computer. Now the only way it powers up is by plugging it in. I also notice that the light that indicates power on the power button and reset button do not light up.
The computer is a VPR Matrix 2020 with an ATX P4 DDR System Board
Thanks for any help you can give me.

[Avooc]

The boot sector of your computer may be messed up from a virus or something of that nature, also the wiring in your computer sounds like it was done incorrectly if the light is not working.